I saw some spider webs on one of the plants and my son found some spiders nearby, so I assume something must have laid eggs (although I didn't see any raised surface). I looked at nearby plants. An azalea and a clematis both have similar spots that are brown, not yellow, so I hadn't noticed them.
On the Rose of Sharon, some of the leaves are now curling up, but also new leaves are coming in and they look fine. Which validates the egg-laying theory. So. I sprayed two of the Rose of Sharon with an insect spray. (I also hoped to use something homemade and organic but didn't want to wait). I agree they are tough. They are faring much better in 100 degree heat than I am!
