How much coop/run space do you have for all of them?
Some birds are more timid than the others so they don't get food/water like they need.
I keep out 2 water stations and have multiple feed stations - seems to help for me.
Are the urates tinted yellow or is that the lighting?
She may just be dehydrated/not been eating if she's being bullied away from food/water, but usually there is a reason for that (not enough space, the chicken is not well, etc.)
Taking a poop sample to your vet for testing would be a good...
Can you get some photos of her and her poop?
Check her crop to see what that's like.
Have you felt inside her vent for an egg?
Look inside her beak for obstruction, mucous or lesions like canker.
You may want to take her aside and see if she will drink for you. She may be dehydrated.
I...