Chickens losing feathers

[Richely]

Hi, my chickens have red sore patches where they are losing feathers, I don't find the feathers and haven't seen them pulling out feathers and there's no signs of bullying, they all seem to get on with each other well..they are around 1.5 years old and healthy otherwise, eating, drinking and laying eggs, all seem bright and happy..it started about 6 mths ago with one in particular who has lost them on her back and underneath...
i have dosed them with Harkamectin, powdered them with diatomaceous earth and sprayed with gold label iodine spray...I can't see any parasites...also bug sprayed their house (while they slept somewhere else). I also increased their protein (turkey pellets), and added sunflower seeds to their corn...they have a large house and run and I work from home so let them roam the garden in the afternoons, so they shouldn't be bored...at a loss as to what is causing it...I did change house litter from the usual wood chippings to another supplier which smell slightly scented, but I use hay in their nest box and so I'm assuming they don't have that much contact with chippings...any suggestions much appreciated ...Thanks

 

[sourland]

They are feather pecking/plucking. It generally starts when birds are crowded and bored (winter when they are coop bound frequently). Do an on site search on Pin Less Peepers. They can be used until feathers have regrown. This habit can be broken.

 

[Richely]

They are feather pecking/plucking. It generally starts when birds are crowded and bored (winter when they are coop bound frequently). Do an on site search on Pin Less Peepers. They can be used until feathers have regrown. This habit can be broken.

Thanks Sourland, I haven't seen these before, I will give them a go

 

[Kriscam]

I'm having the same dilemma. I can't figure out what is causing this or how to treat it. I've run through every scenario - I can't find any parasites on her, she's not broody or molting and is acting normally in every way. No recent changes to any routine or feed. Has a super clean environment and smooth perches. Is high on the pecking order and I've not seen any aggressive behavior from her flock mates toward her. Even if there was - could they pick feathers from her belly? Should I treat this irritated skin somehow? It looks painful. Could it be a staph infection?