Look @ week13 diary & pix.Leaves almost entirely o...

Hello @mulch ! It looks like with nutrient burn ( using fulvic acids like bio-ag can lead to nutrient burn even at low EC values ) It also looks like with a calcium deficiency or it could be potassium deficiency ( coco contains potassium which is chemically bound with coco and released at later stage and that can lead to potassium toxicity ) but with that kind of lights its really hard to tell. Anyway you should not worry about it since they are at the end of their life. In fact it looks like you should have already harvest. The buds showing signs of fox tailing due to over maturation. You better start flushing and harvest. Happy growing ! 👊

First, purple pictures makes imposible to tell the real colors of the leaves. To me it looks like nute burn plain and simple. For coco that run off EC is too high. I know you don't want to, but I would really consider a thorough flush, if that's not a possibility, then lower your feed strength to 0.5 EC (250 PPM)

What I don't like is that cupping that the leaves are doing, you're using a host of enzymes, bacteria etc so i cant see root rot being in question. Thing is maybe the coco is buffering out to a higher PH in some pots, if PH is a tiny bit lower it could cause it to fluctuate. If you're using buffered coco it could be that. Yet I think that lamp to plant distance might have something to do with it, seems like the affected plants are all under the same light or wind corridor ? If so just dialing those back a bit will basically fix it. You can go ahead and carefully pluck the leaves that are damaged beyond repair 70%+ and see if and where new leaves are affected so you can sort of start ruling things out (look likes K deficiency sometimes... almost always nute companies put a lot of P in and not enough K for some reason) . Good luck man + thanks for killer descriptions + deets 🚀