lost all neck feathers within 24 hours

[endo12]

This is a two year old flock of Black Austrolorps and Buff Orpingtons. This morning one of the Black Austrolorps has no feathers on her neck. No blood is obvious. She seems to move in and out among the others when I put down scratch this morning. All the others in the flock (7 chickens total) seem fine. Too early for molting I think, so worried she might have been attacked by another hen (no rooster). What should I do? Any ideas on what might be happening?

 

[Indiana hens]

Did u check for lice?