Hello fellow aquapons.  Gotta quick question for you very knowledgeable folks out there. The lettuce in our system has had a few problems as of late, and I'm not sure what is going on.   It seems that only the older leaves are affected, and it starts with a general interveinal chlorosis, then the tips burn, then a bronzing / leathery thing happens.  They are very quick to wilt when it's hot, the…