Neck is red and featherless

[Campesina]

One of my hens has a red , featherless neck. She is eating, drinking and otherwise acting normal. It has been like this for about 2 weeks.
Should I be worried??

 

[sourland]

A flock mate is over grooming - feather pecking/plucking her neck.

 

[Campesina]

I haven't seen that..should I medicate somehow?