I suspect midge (it's a tiny, tiny insect) too. Some folks are trying
Triazacide as a replacement for the diazanon. You have to put down the
insecticide as per the directions, and you have to be diligent about it. Midge
has a 3 - 5 day hatching cycle.

HTs take 6 - 8 weeks to rebloom, so if you had a bloom cycle already, it
probably finished in mid-June, next bloom in late July/early August.