Usually a sign if heat stress. You may have a tempermental strain.
Mine has shown this sign a lot I tend to not worry about it being there is always so much new growth almost daily, constantly trimming 2-5 leaves off my girl per day even though I shouldn’t in flower correct @Todd.grobo or is it ok to trim a few off everyday?
They say to not trim much during flower, but I hit mine good after the ph problem last night. I took off a bunch of lower stuff and some of the brown leaves up top. Might push back flower a week, not sure yet.
I cut daily. Not much but I will snip a few fan leaves each day. Always clearing a path for light. I don’t think it hurts or slows the plant.
I don’t like to do the big huge chop day. That seems like a shocker to me. Just my opinion. As long as you are careful, you will still harvest flowers 
The way it is looking I will have a huge center cola I am going to guess she will be 3.5-5 grams hopefully, shoot that cola alone will last me damn near a month smoking wise 
Flower : day 19/41
Average temp: 23-24c
Average humidity: 53-55% (can’t seem to lower it much more)
She’s starting to smell delicious 
Update on the leaves - I implemented a fresh water change (only been using distilled - costs a fortune here but worth it) and suspect the grobo recalibrated the nutes and there’s very few affected leaves now. I just keep taking one or two out each day. I also did a decent defoliation yesterday as well. Also pushed the tallest cola away directly from the lamp, hopefully that will buy some time but I also have LST clips if needed.
Looks good, but maybe a good bit more can still be taken off. You can see not much light is getting down lower and you can’t even really see what is down there.
OK thanks @TheDogMan appreciate the tips! How aggressive would you go, as I have seen some vids of the fan leaves stripped back to essentially just the colas themselves! This strain seems to handle defoliation quite well - she doesn’t stop growing no matter what I seem to do.
I only trim the big ones, but enough so you can get light down below. Some go the entire “cut everything off but the top foot” 
but I don’t go that far.
Mostly up too you, I just like to cut enough so light gets down lower.
Mine likes it 54%
@Willcol1 How much does Distilled run you? I can’t imagine it is more than a $1 per gallon? Also she is looking amazing
Looks great 
Can’t buy it in stores in the Uk, I am paying £30 per 25 L (5.5 gallons)… so call it $7 per gallon
I been reading up and many places say using tap water is fine, so all I been using since I returned that RO system. I run it thru it an 8 stage counter top filter that removes chlorine, lead and things like that. Then I let it sit out anyways for 2 days, as many say to let it sit 1-2 days. I have a couple buckets sitting out now.
Holy smokes man, that is absolutely absurd my friend!
She is amazing
Looks great