Phlox leaves Jeanna phlox
I can't really tell from the leaves, but the leaf curl and spots could come from a fungus or from insect pests that may be on the undersides of the leaves. Turn the leaves over and check with a magnifying glass for small insects. If you find insects, wash off well with the hose and then spray with an insecticidal soap mixture or neem oil (available at garden center and hardware stores), getting it on the undersides where those insects are. You can also pick off the worst affected leaves and discard in the trash.
Thank you for contacting Cooperative Extension,
What should I do if it is a fungus? you
You could send a sample in for me to look at under the microscope. The drop-off is located at 461 Wyoming Road in Newark at the Cooperative Extension Office there. The neem oil I recommended will also help control powdery mildew, which is the most common fungal disease we see on phlox.