What's wrong

[19marvinn]

Her butt feathers are all gone. It looks rough.
What do you guys think?

 

[Isaac 0]

That could be the others chickens pecking at it explains why it is irritated or it could be lice/mites.Chickens peck each other when there is a lack of space.I would check for mites/lice.

 

[Eggcessive]

Get some BluKote at the feed store and spray her bare spot every 2 days until the feathers grow in. Make sure they are getting,enough protein in their diet, that they are not over crowded and not getting bored. Separate any bullies.