Chicken walking funny and keeps laying down

[LazytownChick]

A few days ago I noticed my EE was waddling around and laying down a lot. The other hens started bullying her so I brought her inside and made a makeshift pen for her. I have her vitamin B in her water and some nutri-drench. It seems to have given her energy and she's walking around more but will still lay down. She has a healthy appetite and is eating well. Poops look normal. What could this be and what else can I do?

 

[PDXJULES]

Are her feet normally that dark, or could her foot have frostbite?

 

[Eggcessive]

How old is she? Can you can a close up picture of her legs, feet and toes? It does look lie her feet are very dark, so I would like to rule out frostbite. Her tail position is down, and that sometimes can be a sign of a reproductive disorder. Has she laid eggs recently? It is good that she is eating and drinking.