My older hen Blacky, a black sexlink, had been laying very well until about 2 weeks ago, when she started having loose green stools, not eating very well, and stopped laying. My other 4 birds are fine. She still roams around with the others, just seems slow and careful when she walks, and she seems to have a hard time getting up and down stairs and up onto her roost. She is even refusing her favorite treat, sunflower seeds, just looks at them and turns her head. This began at about the same time my youngest pullet began setting on a clutch of eggs. Any connection? Any ideas? I'm worried! Does this warrant a vet visit?