My phlox David is dropping lower leaves after they turn yellow. They have spots on them. I thought they were supposed to be disease resistant? It used to be in an area that only got 2 hours of sun, and it always looked fine then, it just didn't grow or bloom that much. I moved it last fall, and I thought it would be more vigorous in a sunnier spot, but it definitely doesn't look healthier.

My other phlox look great.

Deanna