It's not wilt, because the plant is well....not wilted :-) And I'd hesitate to call it "acutely ill" - it has a bit of leaf spot, nothing more. While this does tend to be fungal in nature, I'm not sure I'd go out of my way to address it. If you treat for powdery mildew, go ahead and include this in the program. It's not fatal, usually weather related, mostly cosmetic and nothing to get too excited about.

Thank you very much, gardengal. We were pretty upset at the thought that we would have to cut them all down.

Thanks again!