Frostbite?

I have just bought a sliver Sussex pullet over the weekend along with 5 others (4 bought one day 2 the following day) but my sliver Sussex Hecate her comb and wattle are black/ have black spots on them, 2 others have tiny black spots on their comb and wattles but nothing like what Hecate has. I have read that chickens can draw heat from their feet,comb and wattles so the rest of them will stay warm and that's why feet,comb and wattle are effected by frostbite that and a poorly ventilated coop are like a perfect storm.I also new to owning chickens and have read what I can but most books or magazines here in the UK (well the more recent mags) don't touch on the subject other then a few sentences and no pictures. Any ideas? Oh I also washed and dried her comb and wattle to make sure it's not blood or dirt and it's not either