I noticed today that about 3 of our girls have some darkness on their combs, one with quite a bit. We will be increasing the ventilation to our coop to help. Is there anything I can put on it to help heal it? I know you can put things like Vaseline to help prevent it. They are RSL and have pretty good size combs, a few of them have lost some tips on their comb. We have a few nights of -20 windchill. They have a fully insulated coop. I'm pretty sure it's because they need better ventilation, that will be done today!