Does any of the black - look like it could be bluish to you. When there are blue tones to the darkening, it can indicate heart problem. Have you checked all over for any other symptoms? lice, mites etc. Any changes in output? Any respiratory distress. If it is a blackish color it could be due to cold weather temperatures. It then would be frost bite and then that part of the comb would fall off. It is unusual that only one would have gotten frostbit while all the others did not.... Is the weight of this one less than the others?
Weight is good, no sign of lice or mites and output normal ...it does seem to have a bit of a bluish tint to it. If hart problems what possible treatments could I be looking at?
Also it is soft like a normal comb would be like, not hard like you would find in frost bite. Also the dark color started on the front of her comb by her beak and has moved back over the last couple of Weeks. I was thinking blood circulation problems. But am not sure. Mostly just hoping it's not contagious. She seems healthy otherwise