Help! Blue Eyed Lucy with black dots and I don't know if it's mites or something else

[IHaveADogToo]

Charles here is a Super Mojave. Just a few days ago I noticed what looked like black specks in this one spot on his back. At first I thought it might be mites, but then I realized I couldn't wipe them off and they didn't come off when I soaked him, either. He just shed yesterday and the black dots are gone, but now they're red dots. When I zoom in with the camera it looks like irritation between the scales and on the tips of the scales. See attached photo.

This is his second shed with me. It was a complete shed, all in one piece, eye caps and all. His first time shedding for me something similar happened. He developed some black dots in one spot by his mouth that, at first, I thought were mites, but they didn't move at all, and they went away when he shed. It didn't turn red like this time. Also, last time, it was another good, complete shed. That was over a month ago, no black dots at all since then, until just a few days ago, before this shed.

I know I keep dismissing mites... but... is it? Like I said, I never see the black dots move. They don't wipe off, or come off when he soaks. But they come off with his shed. I've never dealt with mites before, but from what I've heard that doesn't sound like mites. I'm also hesitant to say it's mites because I have springtails and isopods in the enclosure. I'm no expert but I've been told they eat mite eggs? But I don't know what else this could be. Is this just something weird he does when he sheds? Why do his scales look irritated? Is this maybe scale rot? I recently realized I've been keeping his humidity too high, and I've had him for a few months. Maybe that could be what's happening? His humidity has been closer to 65% and sometimes even 75% pretty much this entire time.

This is my first snake and I'm doing my best, but I clearly have a lot to learn. That is why I'm here for help. I'll correct the humidity issue regardless, now that I realize I've been doing that wrong, but what do you more experienced snake keepers think these spots may be?

To be clear, there are no black spots on him now since this shed, just these red spots.