Yellow

maybe N.. no info on what you fed it. so it'd be just a guess. The rest assumes that it is related to N, but you need more information to be certain. pH is important, 6 is fine. optimal ratios will be relative to pH a bit. e.g A lower pH may need a bit more N, higher may need a little less N etc... just generalized example, not necessarily about your plant here. 5.8-7 won't kill a plant and it can grow well. what is optimal? fuck if i know. my nutes are buffered, so it's the same pH all the time and i don't have to think about it. keep it consistent, and you'lll find that balance sooner. one less floating factor muddying the waters. senescence is a thing.. the plant will naturally die slowly at some point late in flower. This can result in an overal degradation of the canopy. I would wager this is some "Bloom" formula or mix that shorts N too much for some inane reason (based on popularity of a belief and not facts)... and if so, the proof is in the pudding from this picture. If the plant isn't getting enough N, it goes yellow from bottom up on plant and tip-in on leaf - *not interveinal. If pH is okay, that means it doesn't have enough N. Despite feelings on the subject, the plant needs N throughout its life cycle and not in hugely varying degrees. could there be different needs at different points? sure, but nothing drastic. cellular growth is still made of similar building blocks despite different functions relative to a plant, which is a fairly simple lifeform.... probably animals too for that matter. When you see a plant get too dark, you can dial back the N. (among other possible causes, but assuming N-related issues only for simplicity.) If it doesn't get dark, it's using it at the rate you are giving it (or pale for that matter). if it is using it up as it is taken in, that's a good thing. if it gets pale as described above, it needs more... doesn't matter if it is flower or vege.. the plant simply needs more. it cares not for these labels or feelings on the subject. if someone's bloom formula doesn't result in pale leaves in flower, then it's fine.. don't get hung up on syntax. Either it has enough of each molecule or it does not.. .call it whatever you want. our tech and knowledge resolves this stuff down to the atom...