3 out of my 21 babies have feather missing above there tail. Help? We have no roosters only females. They are between 20-24 weeks old

[HeatherKellyB]

You could try to increase their protein and if that doesn't work, you'll know it's a space issue. Even if they free range during the day, they need 4sqft per bird inside the coop. Some require more space than others and will peck, bite and pluck anyone that attempts to roost near them (learned this from experience). The feathers that have been plucked will grow back fairly soon. Feathers that are broken won't grow back until their first molt. I wish you the very best

 

[aart]

Crowding stress and maybe low nutrition.

Both coop and run are too small.
Doesn't matter if they free range at time.

How long have you been feeding layer feed?

@aart has a good way of explaining checking for mites or lice.

I doubt this is bugs, but....
My Bug Check notes:
Have you checked them over real well for mites and/or lice?

Google images of lice/mites and their eggs before the inspection so you'll know what you're looking for.

Part the feathers right down to the skin around vent, head/neck and under wings.

Best done well after dark with a strong flashlight/headlight, easier to 'catch' bird and also to check for the mites that live in structure and only come out at night to feed off roosting birds.

Wipe a white paper towel along the underside of roost to look for red smears(smashed well fed mites).

Good post about mite ID by Lady McCamley:
https://www.backyardchickens.com/threads/my-chicken-has-mites-now-what.1273674/page-2#post-20483008