That is just normal, no matter what because there double rex they will get cuts and scabs. It's from playing, wood chips (wood chips always seem to cut them up the worst), or just being rough with each other. I really woudent worry unless theres puss coming out of the cuts, blood all over, or a Massive cut on them. If your still to worried about them, put them in separate cages with care fresh. Hope this helps and I wish you the best of luck with your bald ones.