Hen with mareks
I'm sorry you are having trouble.
Could you possibly have one tested to make sure Marek's is what you are dealing with?
I do recommend that you read at least the first link provided. It is long, but has useful information, a good overview of Marek's and other illnesses/disorders that have similar symptoms/signs of Marek's. As far as what to do, that will ultimately be your decision. Marek's can survive for a long time in the environment, so there will be a risk of other birds getting it in the future, this is also covered in the same article.
Hope it helps.
Edited by Wyorp Rock - 3/5/16 at 9:15pm