hey - I just found this yesterday while researching my chicken illness. If you want the PDF, email me and I will send. I found it quite helpfull! these are on my photobucket site.
I am not a veterinarian but I am lucky enough to live near several that are avian capable. We have been keeping chickens for maybe 8 years now and continue to learn. I wish I could help with a specific remedy but I cannot. I know the heartache that comes with watching one of your girls ailing. We were recently baffled and heartbroken by the sudden decline of my favourite hen "B.B."
A local (very compassionate and caring) vet took her in and suggested some meds and an x-Ray. The x-Ray showed the source of her problem. She had eaten 2 wood screws and a thumbtack. Sadly, I decided to put her down to avoid further suffering. I bought a magnetic sweeper and cleared the yard to protect my other hen from the same hazard. Yet another lesson learned. It sounds like you have tried many things. I hope you find the problem and your girl gets better. We have learned that, as with any pet, one gets emotionally attached to chickens and sometimes your heart gets broken. We can only strive to give them a healthy happy life and be ready to let go if the unthinkable happens. I wish I could be of more,help.