Do you have Rooster Booster vitamin B complex on hand? I might treat her with that and see if it helps. I'm assuming there is a dosage on the bottle, because I personally don't know and have never used it. It wont hurt even if that isn't the issue.
What is the ratio of feed to corn/scratch if you had to guess? Mixing feed with seeds and corn isn't really a healthy diet. I think its a common misconception that it is, but really, seeds and corn have very very little nutritional value, and are very high in fat. This offsets all the nutrients...
I don't have much experience here, but I do know this doesn't sound like the Avian Influenza. The symptoms are very different.
What do you feed? Could it be a vitamin deficiency? I agree that a video would be helpful. To post a video, upload it to Youtube or another video platform. Then post...