Frequently soaking?

[MissterDog]

That's the surface temp. I use a temp gun to read my temps.

When I'm not home, the cold side temps can drop to 75. But they pick back up to 77-80. His cool side hide is 78 degrees when it picks up.

Could be you're right and it's because he's shedding. I'd still keep checking for mites just in case but it's likely you've already obliterated them with PAM before an infestation broke out. Something to keep in mind is only adult mites are black. Babies/younger ones are white and sometimes resemble dust or salt. So that's something else to look for.

I'd say just keep an eye on him and see if he continues this behavior after he sheds.