Sometimes yellow poop means nothing. But yellow poop and a shriveled comb can mean infection. Yellow poop can be a liver infection of some sort. It can also mean worms. Has she been wormed lately?
If she has already been wormed, I would start her on some antibiotics. Sulfa drugs work well on liver infections. Tetracyclines like Duramycin works on other internal organ infections. You may need to feed her what ever she will eat just to keep weight on.
I have a hen that stopped eating and drinking, had yellow urates, lost a ton of weight. She had some sort of liver infection. I got her on some sulfadimethoxine. You can't keep them on sulfa drugs for very long. So I ended up treating her again a few weeks later. She recovered completely.
Oh, and welcome to BYC!
