Ooooook Bingo, just saw your journal. Being in soil, following ml2242's advice is ok. But from your last post in your journal, looks like you might have things under control. As far as the cause...it's possible you overdosed your plants and you were stacking nutes in your soil. Remember the addition of nutes=lower PH. So if you're feeding more than they're eating, and not flushing properly/regularly...then your nutes are stacking dropping your soil's PH. With that being said, make sure you sort out that PH issue before administering nutes again or you will be right back where you started.

The wrinkling on your leaves is most likely from the PH fluctuations you are observing.
Jury is still out on your brown spots, could be a CA def...not sure though. That is the first thing that comes to mind. As Marty suggested, a good CA/MG is a good thing if you're using R/O or distilled water. Just watch your nute levels. Cannabis doesn't need as much food as many think, and not nearly the amount suggested by the nute companies. Remember...they're in business. The more you use, the more you buy.

Last bit 'o advice from me: move those box fans. Cannabis likes air flow, but I have found it does not like that much blowing directly on them. Believe it or not, I have actually (for lack of a better term) "windburned" a couple of my plants from direct blowing air. Nothing major, more interesting than anything. Just wanted to give you a heads up.