Featherz, how much of there combs can get frost bite and fall off before, I have to start being concerned about gang green? Of the four NH Red hens all have at least one black tip to there comb, two have every tip white or black! I have a Decon at my church that lives on the East side of Derry (Southern New Hampshire). His Roos every winter would get frost bite on there comb or waddle. He said eveery time Spring rolled around the frost bite would get to them they would start acting crazy, running in circles, attaching walls etc.
Tell him to get more ventilation in his coop and he'll start seeing less of that. Ventilation up above and also down below...he'll want to create an updraft of fresh air to move the stale, humid air out.