Hens bottoms red and featherless

[Bucky182]

I have several hens who do not have any feathers around thier vents and the skin is really red. I would say about a 2-3 inch circle is this normal? If not what could be causing it? Mostly in 12-14 month old red sexlink hens. My Indian Rivers do not seem to have this problem.

 

[monita]

you need to treat all of your birds for mites.