The grobo determines whether or not to use bottle #5 (the cal/mag) based on the EC/PPM (TDS) of the water at the time of filling. If it looks like it is distilled or tap water (the EC/PPM is greater than some value) it will not dispense from bottle #5.
The one thing you’ll definitely find prevalent in most advice here is that it almost always depends on your specific environment to some extent. You can tune for RO water, or tune for tap water, or tune for somewhere inbetween… finding “what works for you” is a big part of the battle.
Your tap water (and what does or doesn’t get filtered) is an immediate example of that; there can be iron and other elements that will vary from one water source to another which in some cases can invalidate perfectly good advice (worked in one area but not another). I tried a handful of sources until I just settled on one and kept that parameter constant to dial in others. If she’s been drinking the water and growing up to this point there’s probably not any problem with the water so much as the level of cal/mag she requires.
I’ve found with DWC that things seem to manifest quickly, but can also be resolved as quickly. Waiting the weekend for a response might seem like an eternity but once corrective action is taken it won’t be long until you see the results. If you still see new growth occurring (topmost leaves getting bigger) and she isn’t curling into a ball then it’s not really cause for major concern yet.
FYI If you have a dropper or something you could add a few mL (literally; 1-3mL) of bottle #5 as a means to add cal/mag.