Mites or molten?

[Vaper]

These are not my birds, but this is exactly what they look like, losing feathers under their butt and the back. I have dusted the entire coop with the diatomaceous earth and I’m going to buy some Sevin insect killer today. This is my first year raising chickens I have seven hands, and one rooster

 

[coach723]

The one missing the back feathers is likely rooster damage. 7 hens to one roo is a little light on hens, the more submissive hens will get more attention and get beat up by the roo. He causes the feather loss when he mounts them. They also may lose feathers on the back of their heads where he grabs with his beak. Bare butts is usually from feather picking on the roosts. Either from over crowding or roosts that are not roomy enough or not spaced far enough apart. The nicest looking bird is often the one doing the feather picking.

 

[Vaper]

Ok thank you for the insight. I’m raising up three more hens to add to my flock is 10 enough for one rooster, as well as finishing a new coop it is 4’x8’ the old one was 4x4

 

[coach723]

10 is a good average number, but it really depends on the birds themselves. You will need to observe, make sure it's working. Roo's vary a lot, age matters too, if he's immature, then it may get better as he matures. 4 x 8 is a good size for that number of birds, just make sure roosts are placed so that birds aren't butt to nose when they roost, either spaced by distance or height to help prevent that. Some birds like to snuggle with others, other birds demand their own space. So too much space is always better than not enough. Your hen/pullets feathers may not grow back until she molts, a chicken saddle/apron can help protect them, if needed, link below. You can also make your own.
http://www.hensaver.com/FAQ.html