White debris on plant leaves is often an indication of an aphid problem. They routinely molt and shed their exoskeletons. In fact, live aphids look to be present in the first photo. Are the leaves at all sticky?

not sticky at all. but aphids were my first thought. And the fact they were on the hibiscus a couple of weeks ago and no sign of them on it now confused me

Ill just treat them all

Diann, aphids can clearly be observed in the first image, as gardengal says....these particular ones seem to be gray, but aphids come in several colors. You need to learn what they look like because they are easy to get rid of with plain water and/or squishing when there's just a few of them. They multiply like crazy, though!