My BO has the tips of her comb that are black. Just the tips. She seems fine and is eating and everything but I am a little freaked out by the black. Should I do anything? I have a light in the coop to keep it warm but I suspect she got the frostbite (if that's what it is) during the day because we have been sub-zero in the mornings. What do you think, and how do I treat frostbite?