Very old & established phlox have turned brown and died?

They started with a bit of powdery mildew which is normal but eventually browned and died. Water has been sufficient.They are Tall Garden Phlox.

Very old %26amp; established phlox have turned brown and died?
This is very unusual. Is it possible that they got a dose of chemical? I live in town, so I never expect to have chemical problems. However, last summer, I had three deformed tomato plants. They clearly had a dose of some type of chemical, probably from a passing ag plane with a slight drip.





I wish I had solid advice for you, but I cannot without a look -- and maybe not even then. I think I would cut it back and try Miracle Gro. At this point, that can't hurt, and it might accidentally help.





Rain