Has she started laying yet? Do you have any cocks/cockerels in the coop? If she is close to laying or recently started and you have any boys in the coop, especially young, hormone-filled ones, they may be harassing her to the point that she can not get anything to eat or drink. Pick her up and see if she feels light. I would get her some good organic, plain yogurt (homemade kefir is even better if you have access to some) and mix it with some hard-boiled egg yolks. Mix some in with a little of her regular feed. Try to hand feed her a few times a day to make sure she is getting enough. Also make sure to give her water. It could be cocci again if she was not affected enough the first time through to build up an immunity or it may be a different strain than the first time. You could treat her for cocci again. I don't think it would hurt her. Good luck and let us know how she does.