So this happened to my squash plants.... Apparently its a very common problem caused by too much moisture and lack of sun to dry off the leaves. It is some sort of fungus and can be treated with various fungicides. Not sure what I'll do... But the best solution is, of course, prevention. SO next year I'm going to move the squash at my house to where there's more sun and CERTAINLY not in my other plot where I'm pretty sure it spread from another persons plot to mine! Spores fly! Poop!