Tiny white spots on herb leaves

Tiny white spots on herb leaves

Hi all! First time gardener and first post here. During weekends this May, I've transplanted seedlings of several herbs into styrofoam boxes with plenty of drainage holes filled with a 2-inch deep layer of one-inch pieces of broken up styrofoam on the bottom, topped with enough potting soil to fill up to 3/4 of the box. Recently, I've spotted many white spots on the leaves, especially the ones near the top, of my spearmint, peppermint, tarragon, and thyme: 1. Can anyone identify these spots? Pest, disease, nutrition/sun/air/soil/temperature problem? 2. Can the infected (?) leaves be used in cooking? Update: It rained at least half a day on the 26th and most of the dots went away. One of the previously white spot-infected peppermint leaves have 2 tiny cuts in it. They aren't holes and no part of that leaf is missing; it seems more like it was torn by someone or something. On a separate note, is it okay to propagate my rosemary now? It is also one of the seedlings I transplanted a few weeks ago. The first frost here arrives on October 6th, theoretically.
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