Gee. It's nice to see an experienced gardener at work. But excuses will kill your ladies. Obviously there's something amiss, and I'm willing to bet it's more than one thing. Reading your troubleshooting form, I could easily spot a few potential issues (despite your protestations) that would be most gardeners starting point. But imagine how in-depth we could have gotten were you to have filled the form out to the best of your ability and with all the facts. I'm sure there's a lesson in here. Just not sure how to recognize it. Any ideas...?

Anyway, I'm in here often, and am quite familiar with a number of different growing methods and styles, and although I'm not a hydro guy, I can recognize when someone is attempting a technique or two that can be counter-productive in the growroom. Let alone all the leaf-stress you add continualy with the nutrient fogger, bug stuff, high humidity...on what appears to be on a daily basis. You mention humidity isn't an issue, but according to answer 'T' from the form, you are at 55% (ish) average, plus fogging and spraying. Yes...humidity and respritory stress is an issue.

Can we make this easier...? Which technique(s) did you add to your growroom strategy after your last successful crop? (nutrient fogger, CO2 sprays...chosing what dilution is best and not following instructions...new bug sprays...) What additives did you start or stop since your last successful crop?

Also, there's a link in my signature regarding plant myths. If you would be so kind as to at least read the link I placed below?
Foliar Feeding Myths
Despite being an agricultural refrence, the basic plant biology is the same.

Or, wait till someone else (with more experience than I) chooses to chime-in. It might well be that you are right. After all...I'm just filling-in for the hydro guys, and it might just be a ph thing.