feather loss

[lee1973]

I have 6 well looked after 10 month old chickens in a large run with a hen house 3 of them have started to lose feathers on their stomach and one of them on her legs . They have a good diet of fresh greens , rice ,even pasta, pellets , corn and oats on cold days I cant see any signs of mites although the weather is starting to warmer as spring starts. The skin is pink and i have noticed that i have only had 5 eggs for the last 2 days when i was getting 6 without fail. the run got a bit muddy when we had lots of rain recently and they did get a bit muddy could they have pulled the mud encrusted feathers out , I have since relayed bark chips and the run is much better for them.the also go out daily in the garden to eat grass

 

[Marshchick]

I've noticed the exact same thing with my 10 month olds. They're very healthy (so it seems) and they're starting to lose feathers on the backs right by their tails. Egg production is about 1/2 what it was (I have 11 hens and 1 roo). I can't see any mites, and no sign of blood. Just them losing feathers and low egg count.

Any ideas what causes this?