Chicken won't gain mass

[Chuchucola1]

Hi,
I have been a chicken Mom for 5 years now and have an issue I have never encountered. I have a Rhode Island Red hen that is approximately 3 years old. I noticed she was lethargic and picked her up to examine her. I wanted to cry...her breast was nothing but bone...I immediately brought her inside and out her in her own cage. This has been over a month ago. I put her in medicated chick starter to no avail. She has been eating 16% laying pellets for the past week. When she eats, it is though she isn't picking up the food just raking it backwards with her beak. I know she eats but she WILL NOT gain any mass in her breast area. She has not laid an egg since she has been inside. She is very alert but her comb is kind of drooping to the side. Her color looks fine and her poop is normal...I am at a loss for what to do. Any help would be greatly appreciated.

 

[pennyJo1960]

Good Morning can you post photos of her please the rode island red is not a beefy bird,

 

[coach723]

Are you able to ever feel anything in her crop? Is it always empty, or is it hard, soft and squishy etc?

Do you know if she was laying regularly before you brought her inside?
Feel her abdomen, below the vent, between the legs, does it feel bloated at all, either very firm, or water balloon like? Compare with a healthy bird if you aren't sure.