Chickens losing feathers?

We have 6 chickens and we've noticed that 4 of them have lost all the feathers around their bum area. It's odd because the chickens who have lost feathers in these areas have lost them all in exactly the same places and they are all the same size of lost feathers. But not ALL our chickens have lost their feathers! We know it's not an alpha thing because the top 3 alpha-most hens have lost their feathers as well as the bottom ones. The only ones left untouched (for the time being) seem to be the ones in the middle of the pecking order.

We are also noticing a decline in eggs. We were getting up to 6 a day about 2-3 months ago and now we are only getting 3, SOMETIMES 4 eggs.

We've looked for mites but don't see any and there doesn't seem to be any sign of skin irritation or pecking/scabs. Also there weren't any piles of feathers, they just disappeared (maybe the girls ate them???).

We did start mixing cat food in with their chicken feed (as an extra source of calcium) and now the girls love the cat food more than their own chicken food.

Also just a quick note they are all around 1 year old, didn't molt in the fall.

Here's the layout:

alpha (barred rock): lost feathers
2nd in command (dark golden sexlink): lost feathers (not as much as the others though, at least not yet)
3rd in command (buff orp): lost feathers
middle gal (light golden sexlink): has feathers
the crazy one (wyandotte): has feathers (note: this one was brooding last week but has since stopped due to our intervention ((shutting her out of the nest boxes during the day for 3-4 days)).)
omega (ameraucana): lost feathers (gets picked on a lot in general but can tell she has lost feathers in the same way as the others in addition to what the other girls peck off)

Would pictures be helpful? We really love our girls but are worried! Is it molting? Mites (although we couldn't see any or find any in nestboxes/roosting pole)? Could it be the cat food???

I am going through kinda the same thing. Some have a little more than just the bottoms missing.
Here is my message thread..
bald spots

and my continuing saga...
bald spots update

I see feathers growing back on most. The bald spots are starting to get prickly looking instead of totally smooth and bald. lol

I have a couple who keep getting pecked but I think this is not the original problem. They are now victims of "I see blood so must peck at it" syndrome. I think that I will have to duct tape them up to let the feathers grow back out. Then hopefully their issues will be solved too.

Do you have roosters?? I have heard that roosters can cause that problem with their "favorites"

Nope no roosters! And thanks for the threads, I'm checking them out now

The weird thing is that the ones that have no damage are the ones who just stand around and do nothing. I've watched them a lot too and there is no mounting or pecking or fighting going on, especially not from the ones that are unaffected. But mine look just like your plymouth barred rock one Christie!! (Oh and by the way: my other half is born and raised in O'ahu yay Hawaii)

Do they all roost on the same level? Or are some below the others and able to reach the bald spots? If they aren't all on the same level, the birds on the lower roost might be pulling out the feathers on the ones above them.

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go Hawaii!! Lol!

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One sleeps in the nest box, the others all sleep together on a roost that they jump up on to. Also the one in the nest box is always the first one to bed and she IS one of the 2 that hasn't lost any feathers (her and her bff are in on it together maybe!). I'm not sure if she can reach them from the floor but it would be kinda cool to set up a night camera and find out what IS going on in there at night lol.

I'm going to start letting them out into the yard more. When they were younger they had free range of the yard but with spring planting we've kept them in their run so that they don't dig up all our flower and herb and vegetable gardens. Now I'm monitoring them and a quick spray on the mist setting keeps them out of the gardens. Perhaps they are frustrated at being penned up now.

Also going to try giving them some more enriching things, such as hanging cabbages, making that recipe Christie mentioned in her other thread and buying some sod and sprinkling meal worms in it and putting it in their run for them to scratch at.

I throw high quality bird seed down for mine to scratch for.. keeps 'em busy and usually out of trouble