Help chicken not eating normally or behaving her normal self.

[JSL]

Hello
I have a 3 year old hybrid chicken.
Since Friday she has not been her normal self much quieter and not eating as normal (usually she is a pig). Her poop has been waterey and yellow and her feathers on her back have gone from healthy to raged. She has not laid eggs for over a year.
I have put her and my other chicken who is not sick on worming food and have tried applying diatomaceous earth to her back. I have attached photos of her and her rear end. I would like to treat her myself as there is not a vet who will see chickens near me.

 

[nuthatched]

What's worming food? Diotomaeceous Earth isn't worth anything. What's her diet? She looks like barred rock to me.
It sounds like reproductive infection

 

[JSL]

I feed them layers pellets at the moment I have them on de worming flubvent in their pellets. They forage in the garden for wood lice, ants and a little grass if they are out. when they are in the run I give them kale or greens in a hanging feeder that they can pecking at. I also give them a small amount of mixed corn and black sunflower seeds as a treat but not every day.

They both have the same diet and the other chicken is fine.

she is not any better today, she is spending more time in the chicken coupe than out in the run.