Okay, I'm certainly no expert, but I'll chime in anyway.
My first thought would be to make sure the plant has enough air circulating around it. Is it planted too close to something else? Does it have room to spread and breathe? Then, I'd make sure it wasn't getting too much moisture. Is there a sprinkler located nearby that needs adjusting? You'd think I'd know more about mildew living in Florida, but I don't really see it too much. Come on out people reading this; I know you can help!