I have been watching my Barred Rocks closely. They have dark black spots on there combs. It started out just a black spot here and there on a couple of hens. Not its more wide spead amonst my six hens. one hen has it all one her come and the tips are getting raw. At first I thought it was maybe poop or dirt on it. It looks like scabs, dirt or like a black mold. Does any one know what it could be? Im worried. I dont need to go into winter with this.