The chicks are too young for feathers. The feathers look like they came from the broody - like a molt. She has been with the flock for the whole time. Once hatched, I moved mama & her babies inside a "broody cage' inside the coop/run. (Didn't want to risk her babies getting lost while free ranging in the big outdoors, but still want them to be part of the flock.) I have other black chickens (her former hatch). Since they're 3 months old, they kind of do their own thing, but I would expect mama broody to attack them if she felt danger. Don't know if that happened or if she's just molting. Found black feathers 2-3 days in a row. No other colors -just black.It's a miracle they have not died of a heart attack by now. sounds like PTSD though!
Can you put a camera in the coop to see what is happening with the feathers?
Who is doing what to whom? are the chicks separate or free in the coop. could be dangerous.
I have always had mine in my house in the sun room before I put them in a rabbit hutch outside when fully feathered. Worked for a five years now. Broody hatching only started spring 2014. So I have to do what works for me. I hope the little darlin's recover from their losses.
Cheers
The inside chicks are fine. Since the broody didn't seem to want them, my kids will continue to mother them until they're sold.
One sweet story: While Cookie(broody) was walking her chicks to their daytime run, the emergency sirens went off for monthly testing. She immediately covered her chicks & two other mature hens joined her making a circle with the little chicks inside. When the siren stopped, Cookie continued her journey to their little private run. (As you can see it's a baby play yard.)