Man, i am interested to see what actually fixes this for you but i have to agree, this doesnt look like leaf spot or a fungus to me. Looks like calcium def. plain and simple IMO.
I may have missed it, but are you using RO water by any chance?
Nope , just straight well water. The thing that has been driving me nuts is that I was treating for mag/cal, and all the other usual suspects. That was the problem. I went nuts trying to figure out a nutitianal, or enviromental cause and nothing I did had any real effect on bringing my plants back to their 'happy place', they just kept getting sicker. Flushing, different nutes, everything I did had absolutely no resolution to this issue. When I started treating it as a fungal infection I started to see some positive results. I may not be out of the woods yet, but at least I now think I have a path to follow.