Losing weight and feathers (photos included)

[froghollowfarm]

Below are photos of a Delaware that is losing some featers around the neck and rear end, and has lost weight overall. Our other six hens seem to be fine (there are no roosters), although a black austrolorpe has lost feathers around her rear end.

Any ideas what could be causing this?

 

[Romochickencrazy]

Have you checked them for lice or mites???? That where I would start. Look at the feathers near her vent for small white or off white eggs.

 

[simone jone]

did u find out what happen. I had i white hen with same dirty bottom and neck/ I wormed her but i think it was to late.
will u let me no if u find out what it is.

 

[BackyardCountry]

maybe an unpredicted molt????