Aaaaahhhh. Ok. Hope ur chickens get better! 

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This is exactly what has happened to a couple of my hens...I have a Leghorn and a Barred Rock that have a small, white-ish patch on the tip of one of their comb points...I wondered if it was the first sign of a bit of frost bite....I bought some vaseline the other day...until this cold snap lets up I will probs have to apply some every night. It's been in the low teens to even single digits here in Boise the last few days. My coop isn't drafty, I just think maybe when their combs get a little wet and then they go to bed it freezes.Light frost bite tends to start out whitish, and if it kills some tissue on the comb then it turns black over several days. Finally the dead tissue is shed over time.
I learned about the process with my roosters their first winter.