rusty red spots that cause leaf death
There are bunches of rusty red spots that cause leaf death. Hits virtually overnight on butterfly bush, chinese lanterns, datura, strawflower, turtle head, gooseneck loosestrife, wiegela but not hostas, speedwell, stella d'oro, lantana, lilies and the like.
It sure sounds like a fungus attack called Rust because that is what it looks like is rust. Spraying the plants with a product called Green Cure or one called Milstop will typically take care of the problem.