Help! What is going on with my chicken's neck?

[wendyron]

I have 7 hens (no roosters) and 3 of them have necks that look similar to this. I thought they were molting at first because this happened in the early spring. Now it is October and they still look the same. It looks like the feathers are coming through but so slowly. I thought maybe it was mites or lice but I can't find anything on them and they have looked like this for 5 months are more so wouldn't they be infested by now? They still have nice fluffy butts and no feather loss anywhere else. 4 of my chickens are perfectly fine. I am stumped! Can anyone offer any ideas? Thank you!!

 

[wendyron]

If you zoom in on the pic you can see what I'm talking about a little better. Thank you!!

 

[adrian0227]

It can be many reasons
Lack of protein
Parasites
They are too overcrowded or bored