Sick hen?

[chick peeps]

I have a RIR that has been acting odd in the past couple days. Her eyes are clear and shes attentive but she has been quite lethargic. She fluffs her feathers up a bit away from her body. Her comb has gotten paler and is starting to droop. I also noticed she has green poop residue on her rear. When she is with others in the coop she tends to just stand or lay in the same spot for hours. She does eat and drink. And when i let the others out to get grass she slowly, but surely followed. Idk what to try to or what might be wrong

 

[Wyorp Rock]

Can you take a stool sample to your vet for testing?
When was the last time she laid an egg?
What is you weather like?
Photos of her poop and of what she looks like may be helpful.

Feel her abdomen for any bloat, swelling or feeling of fluid. Check her crop to ensure it's empty by morning. You may want to clean her if she has poop stuck on her, while your at it look through her feathers for any lice or mites.