Is she losing weight? It could be worms, but I'm thinking if she has worms so bad it is causing sickness or depression you would see worms in the poop. That's a sure sign of an overload. I've seen photos of poop like that and the description said it was a sick hen showing undigested food in the stool. I would try to treat with something more broad that Corid. Why don't you try Sulmet? It's for cocci and a few other diseases. I'm wondering if it's cocci, an e-coli infection or something else. If she wasn't acting sick, I would just think heat stress and a high water intake. Is the weather wet or dry where you are at? Does she free range, eat grass, etc?