I have 15 hens + 1 rooster, early this week I noticed 2 hens plus my roo have gotten frostbite on the combs, since I've put them up in the coop, applied Vaseline to all 16 combs and maintained that they not go out of the coop day or night until the frostbite is cured, no heat in coop (I have had 2 friends lose coops and chickens to fires, I won't chance it.) there are 2 vents in coop for fresh air and 2 windows for natural light, they haven't slowed in egg production, coop is a converded yard barn that is 12' by 8'. Am I doing the wrong thing? Am I neglecting them? I don't want the frost bite to get worse, and the temps have been in the teens at night mid 30s at daytime.