There are a bunch of different mites when my possum wrasse was taken out to be treated, mites identical to yours popped up many acropora colonies I had started to have tissue loss once I had a wrasse back in my tank I only see them in my refugium,
-If you have had any strange coral deaths similar in structure it could be the mites but if nothing was been lossed they might just eventually crawl on everything at night gradually increasing population.
I don’t have anything better but when I see them in person they are identical to what your picture showed, mine only seemed to bother sps acropora I have plenty softies and a rock covered in GSP’s that were never bothered. Their are many different mites that look the same but only bother specific corals. At the worst of their problems I would see around 50 mites on each side of glass at night/lights off.
-Have the mites caused any issues recently or still in the tank visibly ?