HELP

I have an approximately 16 week old hen that is growing a bit slower than my other 5 girls.

They’ve been pecking at her from time to time, I’ve sprayed her with no peck spray and an antibiotic spray to help as needed.
She was almost back to being fully feathered until this weekend I looked at my cameras while we were away and the other had a almost completely bare spot on her back — we separated her to a separate coop/run next to the big one and got her some medicine were mixing in her food but I’m worried I’m too late. She’s hardly moved since last night and is now laying almost sideways with her feet up and not picking up her head.

Is she too far gone or is there anything more I can do to try helping her?