Garden Pests and Diseases: Hibiscus yellow leaves, spotted, buds falling off, 1 by Haysdrangea

Haysdrangea wrote:
I thought I had spider mites so sprayed diluted Neem oil all over plant it got better briefly then it started wtih the black spots. So thought I might have a fungus so I sprinkled some bonide garden dust on it. Still it looks rather sick. It was beautiful when I brought it home from WalMart about 30 days ago. I've see now that one should not apply Neem in the sun or before it rains. I may have done that. What can I do to save this? Thank you in advvance!!