my hen has a bald spot

[west7]

my one hen has a bald spot near her tail. we have only three road island reds and a large coop. I noticed yesterday and the other two were pecking at her,
She is a little smaller than the other two but I don't think that this is the reason? we are concerned.
Could someone give some advice please

 

[chickenweirdo1]

Great to have another poultry lover.
She might just be molting. Or it might be because of the other chickens pecking her.