How do the plants look like?
Im on my second cycle of having the mysterious problems with my plants. This is a quote copied from another thread on icmag but its my exact problems. I had been treating my plants for cal/mag deficiencies with no results whatsoever.
"I have the SAME problems either in late veg or early bloom, not long (1-3 weeks) after I put them under HPS light. After they look extremely healthy throughout VEG, I start to see a leaf here and there with random "blotches," generally at or near the leaf edges, then at the tips - patches where the leaf is papery, tan and obviously dead. Then the patches grow larger, progress to all tips of the leaf which often curl (when dead). Then many other leaves start taking on a bit of a sickly look, getting intervenal
chlorosis and becoming more translucent and turning a lighter, more sickly green. Then most of the well-established, healthy fan leaves (middle-aged) all start to "get it" and die of progressively, while the plant continues to grow and put out new shoots on the main growth points."
