I have 20 adult chickens (not including chicks) and they live in an old 15 by 23 (aprx) ft farm shed. Yesterday, I noticed that some of their combs were getting frostbite, since it was 7 degrees, and gave them all a good dose of petroleum jelly. They are still pullets, although they are laying, and will be a year old in March. They did not molt this year. When I picked some of them up, I noticed that about 7 or 8 of them have a bare patch of gnarly skin almost directly under their wattles and above their crop on their neck. What could this possibly be? This cold northern whether has certainly worn them out.... please please please help if you can!