I've noticed both of my rats have several small, dark scabs around their neck and face. Could it be mites? My cellphone camera is garbage so I can't take any clear pictures, but there seem to be small clusters of scabs close together.
Sure sounds like classic mites. You'll need to treat all your rats with Revolution and if you use paper or wood-based bedding then you should probably freeze it 48 hrs before use. If you use Revolution you don't need to do more than your usual cage clean.