Garden Pests and Diseases: my cuphea is sick, 1 by dp72

dp72 wrote:
This is cuphea, either ignea or melvillia. Cigar plant can refer to either, I believe. It is in a container in the blazing Texas sun from mid-morning until the last rays of the sun. I water it only when it becomes dry, but that is often. It did well for several weeks but the leaves are turning dark, almost black. It has not been a profuse bloomer, but it's still blooming. I suspect it is a cultural or environmental problem, but I understood that it was a good choice for hot sunny locations. Any ideas on why this is happening?

TKS

DP