If your paper towels have colored areas it could be where his scale has caught some of it, or possibly dirt or fast has worked it's way into the scale, without blood coming from the dot it may not be a mite, but just in case use a mite spray and lather it in by letting him run around your hands, remove the water bowl for a while as to not contaminate it and clean out his entire enclosure. I wish you and your snakes well.