I haven’t had any chickens who got severe frostbite on feet before. But I think it should be at it’s worst now. The really severe frostbite of toes or feet usually will turn black and dry up, and those dead tips may take a month or more to fall off. To find out if there is a good blood supply you could prick the skin, and if it bleeds, it is alive. When you have the milder type, you may see some peeling of skin over the next couple of weeks. Here is a pretty severe case that was documented over time:
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