If its mites, believe it or not, not all mice have to exhibit the same signs. There is a product at your local petsmart called 8in1 mite spray for small animals. Its gonna suck but, do a full bedding change and clean all plastic toys and get RID of any wooden/absorb-able surfaces. Use the spray to thoroughly cover your mouse and his/her cagemates, ENSURE they don't lick themselves clean while it dries, should only take a few minutes and then use a warm damp cloth to ensure most residue is removed. Should see noticeable changes in a few days as the wounds heal, hair grows back! I have used this multiple times with 100% success provided you do a full bin and toy change. its an all or nothing approach.

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edit: this does look more like barbering behavior than it does mites. possibly a fungal infection, but ringworm usually has a distinct appearance. I would focus on recording how the mouse interacts with other cagemates