Balding chicken,help

[ravenheart]

My year old americana has been loosing feathers under her beak on the neck.An area about 3 inches by 2 in. The skin seems normal to a bit red.The feather are not growing back and it has been a few months,It is now spreading to another chicken.
Does not seem to be any mites.Does not bother her.Could this be chickens picking on each other????Why just under the neck?

 

[BarkerChickens]

I would guess that they are pecking each other.