Please only feed them layers pellets and mash in the mornings, treats are for late afternoons. This way they should get all their nutrients that they need. Bread also swells up inside them and can lead to problems. What does her comb look like? red, pale, floppy etc. Feel under her wing to see if she feels hot - compare her to one of the others. Is she laying yet? Sometimes when they are having trouble laying and about to lay a soft shell egg they can be off for a few days.