sapphire gem chicken

My hen's comb looks like a crusty science experiment: what is this

Oh, a crusty science experiment of a comb, been there, and it's about as unsettling as finding a surprise egg in your shoe. Your Sapphire Gem's comb going from yellow-ish spots to black crusty bumps sounds like a fowl mystery that needs more than a Google deep-dive. You're smart to suspect pecking at first, but the spread to a second hen suggests something else is clucking around. Fowl pox is a strong possibility, and that would mean quarantine for both girls to stop the spread. I've seen this play out, and the "it could be this" rabbit hole is real.