Do you know how to check their crop(s) to see if they have eaten? If you are facing the hen head-on, it is at the very base of her neck, slightly on the left. Get your fingers under her breast feathers, but a bit higher, where her wishbone is. You should be able to feel it expand after she has eaten; it can feel soft like a small water balloon (if she's had much to drink), and you should be able to feel particles of the food in there if she's had anything hard, such as grains, crumbles, etc (whatever you feed her). I find that my hens always have full crops right after I feed them, and when they go to roost. You might see if she has food in there a few times a day to get any idea if she's eating or not.
The location of the crop:
http://www.1976design.com/blog/images/369b.jpg
This hen has a very full crop:
http://phoenicianfarm.files.wordpress.com/2012/03/black-and-red-crop1.jpg