I posted before about the powdery mildew affecting my verbena plants. I have now observed that some leaves have died, and small (1 mm or less) insects are present. They're mobile so not eggs, white and not obviously winged so they may be a larval stage. I'm looking for identification, and whether they are just feeding off dying leaves (in which case why are they still amongst the dead leaves), or caused the leaves to die. I am not seeing them on the healthy leaves. The plants seem otherwise okay, and starting to flower.