Looks a bit like potassium deficiency. K is very important to the plant's immune system function. Do you have a fertilizer with lots of K in it (last #)? Bloom ferts are a good place to look. Mix up a half strength solution of that with a drop of dish soap and do a foliar feed. Also check carefully on the leaves, including UNDER them, to see if there are any larvae on the top or webs and eggs on the bottom.