mites... again?

hi, i'm quite worried over my hedgehog, hertta, recently. sometime ago (around 4-5 months or so) she had mites, we went to the vet and that was taken care of.

however to me it's looking like she may have them again? i don't think there's as much itching and scratching, but when i look at her face really closely, i can see yellow-ish little dots, though i can't see that they would move around.

i don't understand why it would happen so frequently though. am i doing something wrong with cleaning? could it be age related, is that a thing? she is a bit over 4 years old.

back when she had mites the first time, i cleaned the cage, food cups, any bridges etc. she has in the cage, threw away bedding and started trying to wash that more throughly... i feel quite helpless and like i'm failing here so any help or better insight is welcome.