Try coaxing her to eat some scrambled eggs or even yogurt. Her poop looks a bit watery to but it makes sense if she's drinking a lot but not eating. Do you have any vitamin e with selenium on hand or a children's poly vi sol without iron?
If she's not laying on her nest she's not acting broody. If you can, remove her from the group so you can check her over thoroughly. How does her comb and wattle look? Are they red or kind of pale. Can you take pictures of her? Also by separating her you can look at just her poop and let us...