Looks like Frostbite.
You may want to look at post #16 and #17 by @Eggcessive to get some tips about care. https://www.backyardchickens.com/threads/rotting-feet-feet-were-frozen%E2%98%B9%EF%B8%8Fplease-help.1446585/post-24049164
It would be hard to tell how much of the toes/feet they will lose...