Day 21 Sweet Tooth - Lower leaf Burn

This is my first plant with the Grobo though far from my first ever grow, just not in this machine, so it feels brand new.

Today I noticed that I have what appears to be nute burn on the bottom two fan leaves. I have not adjusted the recipe at all and have made every water change as directed by the app using Distilled water only. When I received my Grobo, we discovered that is shipped with a bad PH sensor as it was only dosing to pure acid, thus I lost my first seed. Grobo replaced the probe and took care of the situation. I only mention this because I am shocked to see the leaf burn and am concerned that the PPM meter may be off…

I also noticed a white speckling on the top of the Coco pod and at first thought I had powdery mildew, but the leaves are not showing signs of that, so maybe this is normal for this type of Coco pod and the Grobo? I attached photos below.

Have any of you had this happen and can you please comment with your thoughts on this. I would hate to loose my second plant.

I removed the two leaves, cleaned the top of the grow plate and sanitized carefully its surface with alcohol, just to be certain I have no bad microbes present there. I did not touch the Coco or plant, except to remove the 2 burned leaves. I also completed a water change, about 12 hours earlier than scheduled, but I wanted the machine to recalibrate its PH and chemicals. I’m thinking about ordering a small fan to place on the bottom to circulate more air (just in case there is PM settling), though that plant is still small.

The genetics are Barney’s Farm Feminized Sweet Tooth. I could not find a recipe for this (they were all Autos and this is not an Auto), so I went with the Generic Indica recipe.

Thank you for your time and thoughts!


Is the stem of your plant normal? I am curious, uploading a pic of a spot that looks a little strange to me… especially at where it touches the coco pod

Someone with more XP will have to confirm, it could be fine… looks kinda weak there at the bottom possibly.


From what I’ve seen on this forum, white fungus is typically okay… Green or black mold is bad on the cocopod. Ive seen pictures that look a lot like your coco and people have said they are fine.

Do you have a water temperature gauge, and is your cocopod really wet at all? Are your roots white or off white or are they brown/slimy/have a smell under the lid?

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Is your unit using Bottle #5 ? How much is gone? If you post a pic of your bottles someone can potentially diagnose your pH issues as well as the potential orange spots on your leaves. #1 and #2 will indicate how much the Grobo is correcting pH at this stage in the grow.

All troubleshooting here, again, I am not an expert and I am in my first grow but I’ve been reading a lot of threads on here in the past month and half-ish.

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Thank you for your response, I truly appreciate it! There is no odor from the tank and was none when I changed the water earlier. The roots look healthy, see the pic below.


Great question! I just took a shot of the bottles and marked the lines in Red for easier viewing. 5 is the lowest but I have no idea what is actually in each bottle or how the recipe is calling dose and to what ppm.


Hi @drsteve, I recommend getting a permanent marker and marking the nute bottles after every drain/fill cycle so you know what bottles are being dispensed. I had an issue with bottles # 3,4,5 not dispensing and I had no idea for a while.



Good luck!!

Now that the pics are posted… : @SWSVIC @Bplatinum9 @SilverGrobo @Todd.grobo @VermontGrobo @vegetato @miami5th anyone have some advice ?

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This is an extremely often occurrence and you need not be concerned. The lower leaf damage is actually caused by the interaction of the leaves touching the grow space floor. So long as you are not seeing any discoloring/damage on your new growth, you are in the clear. You did the right thing by removing the leaves, they were no longer adding any benefit to your plants growth/well being. Nutrient usage appears well within range and as you stated @pyromancy, the white growth on the top of the pod is indeed beneficial bacteria.

Upon further review, the base of your stem does appear to be experiencing what is called “damping off” a terminal issue which will cause the demise of your plant. Can you take a closer picture of your stem with flash enabled on your camera so that we can get a better look. Also, can you take a paper towel and press down gently on your cocopod and post a picture showing how much water has been absorbed into the towel. This will confirm the issue and allow us to better assist you in remedying it.


I had feared it looked like damping off to me


You can recover just need to quickly dry out the pod


What about pythium? If that breeds isn’t the only option possibly hydrogen peroxide as a last attempt plus drying the coco ?

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The “white fuzz” is normal and desirable, but if there is a lot of it too early on it’s a sign that the cocopod is too wet (possibly due to high humidity environment in general?). Best thing to do is dry out the top of cocopod somehow and perhaps even push it up slightly/carefully from the bottom so it’s not getting splashed on as much underneath.

  • h2o2 can be as harmful as it is beneficial, it will help to kill off the majority if not all of the bad biological stuff hanging around in coco pod or water, but it will also kill off any of the good stuff (like that beneficial white fuzz that sometimes grows a bit extra on top of the coco pod aka trichoderma).

  • If you use h2o2 it’s important to be prepared to replenish the good stuff, so adding hydroguard to the water and possibly even fixig the trichoderma in the pod afterward. Not doing this just makes it easier for the bad stuff to come back and regain a foothold as there is no longer any defenses.

  • Instead of h2o2, another option (what I try first) is to just overpower the bad stuff with more good stuff, i.e. increase dosage of hydroguard and/or add mycorrhizae (products like great white/orca) to the water and cocopod itself.

I think it looks that way too, good eye! The potential damping off needs to be dealt with first, like @Todd.grobo said - dry out the pod.


Thanks @vegetato for clearing that up.

You’re right. I did read that h2o2 kills almost everything, including the good stuff… How do you go about replacing trichoderma? Is there some kind of way to induce it’s growth?

A couple of products I can think of that contain some trichoderma:

  • Plant Success Revolution Great White Mycorrhizae (not Orca!)
  • Real Growers Recharge

I’ve taken about 1/8-1/4 of a gram of great white (and “Root Rescue Transplanter”) and mixed it with ~50-100mL of water, stirred it up and then dumped it into the cocopod on several grows so far. The first time that was done after having soaked the pod and roots in h2o2 for a while, but now I just default to giving the pod some fresh beneficials before resorting to h2o2.

Great White + Root Rescue is just what I use instead of Recharge, either will have a similar effect.

Gotcha! I kinda like the idea of using some beneficial bacteria up front

I actually have some Recharge… I haven’t used it for anything yet… I read somewhere that it can cause more problems than good if overused, is that correct? I bought it because I thought most of you guys used it here, but I read further and found that a handful have stopped using it…it causes a gunk buildup in the reservoir potentially, right?


If you use it in the res water, and repeatedly, yeah it’ll gunk up the res and stuff in it. It contains molasses as well, which contributes to the gunk and is generally not desirable in hydro.

The other part of the gunk is “carrier material”, the stuff that the biological product was stuck to in order to package it. Every scoop of something you add to the res water is potentially going to land on the floor of the res.

People were following the directions for using it in soil applications, and adding large quantities to the reservoir in a short period. If used at much lower levels it’s not as bad at all, just a little bit of sediment to clean up afterward.

Using it very conservatively in the cocopod is fine as it won’t end up in the res.

I only use the other products because they’re more readily available locally and I already had them on hand. I also like that they can be used separately or together, and don’t have molasses included. I have used them to “brew a tea” with earthworm castings and other things for soil plants in the past.

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Cool :slight_smile: That all makes sense to me. Thanks for clearing that up… Learning some more day by day :slight_smile:

I can imagine anything solid would fall down to the bottom of the water.

Do you mean by combining with water like you had mentioned or by sprinkling it on there in dry form? Just curious. I wouldn’t mind looking into it’s benefits further and thinking about adding some beneficial stuff myself, but I’m currently worried about my coco-pod drying out so putting water on it probably wouldn’t be something I could feel okay about doing currently. Not saying I am planning on going and using Recharge or not, but I’m just curious.

I might look into this too… I guess I don’t understand exactly all the benefits of using in it besides the current situation we’re talking about actually (beneficial bacterias) Is it also plant food? Does it act as a plant immune booster type thing? Etc. The name “Recharge” makes me think it’s like a vitamin boost for a plant, but that term could also mean a medicine to cure an ailment of some sort I would imagine too

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Yes, combine with water. Just at 1/20th the strength it recommends to and with a much smaller amount of water. This makes sure it gets spread more evenly into the cocopod and isn’t just sitting on top. If you can think of the cocopod as a very tiny pot, and that this stuff is made for plants in much larger pots, that might be a simpler way of looking at it. That coco-coir is as important to keep clean and healthy as the roots and res are; the beneficial biological stuff is how that’s done automatically.

It’s primarily used for defense against the bad stuff but it can also provide a bit of a boost, yes.

It’s a symbiotic relationship, the fungi and bacteria take things the plant doesn’t need or want (that bad bacteria might feed off of, or that might even be the bad bacteria itself,) and provides the plant with enzymes and nutrients in return.

Edit: and that last bit explains why your beneficials can mess/react with your nutrients, topic for another day.

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