Tiny brown bugs in sphagnum moss

[etcherkate]

I wonder if someone can help me identify my orchid pests? At least two of my plants have tiny, almost microscopic brown bugs scurrying around in their sphagnum moss. I have a very young paphiopedilum that doesn't have any visible damage on its leaves. There's a tiny bit of white powder on the leaves that looks to me like dust and not insect residue. A bulbophyllum also has bugs, and there does appear to be some damage on the top side of the newest leaf.

These are indoor plants that live on improvised humidity trays. Unfortunately, they're pretty close to a heating vent that blasts all day long.

Any idea what these disgusting critters could be?