Dark green runny poop

[hinkjc]

Internal parasites. With the way she is eating and pale appearance, that would be my guess. Most vets will check for worms for you. It is worth a look.

 

[Oopoo]

I don't think grapes are good for chickens is she at the bottom of the pecking order? You could try what someone else did and "peck" on the chickens that are picking on the weak one.