Why does my chicken have a bare butt??

[MommaHyde]

Out of our six girls this is the only one with a bare butt so I don’t think it is pest related (but could be wrong) it looks bad and I’m very concerned. Her neck feathers also look pecked at or damaged from something else. Need advice on what to do. See pictures

 

[Eggcessive]

Make sure that she does not have any lice or mites under her vent. Here is another thread on this subject with some good links and recommendations:
https://www.backyardchickens.com/threads/a-way-to-deter-pecking-bullying.1318133/