Do you notice undigested grain in her poop? It looks like cracked corn in the poop sample you posted. Is it very hot? Heat stress may be an issue. Also, I recommend taking a poop sample to your vet and ask them to run a fecal float for parasites. Even if a vet doesn't treat chickens, they can still run the fecal test to determine if worms are present. It could be your hen needs worming. But the fecal test would confirm it.