Hi there. It's cold here in western Washington. We're having temperatures going down to about 24 degrees at night. Lots of frost. Our coop is ventilated properly, we are keeping the litter and bedding dry and clean. They have several choices for roosting at night. We have a run that is half covered and half uncovered... with a straw bed under the covering and just leaves/dirt on the uncovered side. We have their heated waterer outside in the covered area and leave their feed inside the coop. I've done research on frostbite, and we were all in agreement here at our house that we shouldn't see any signs of it with our temps and the way the coop is designed and the care we provide to the chickens. But, this morning as I was making my morning social visit, I noticed some discoloration on their combs. Not black or blistery, just a darker color. Is this a sign of frostbite? We have Rhode Island Reds and Astralorps.