could it be bites that got infected? those are definitely not normal-looking mite bites.
you should only be using paper towel as substrate until the issue is 100% taken care, and then wait another few months to ensure nothing creeps back up before switching back to your normal substrate.
i have no first-hand knowledge of mite problems, only what i've researched, but honestly i'd take that animal to a reputable vet; better safe than sorry.