Sorry you lost your chick. Culling chicks is no fun, and one of the harder part of chicken keeping. Sometimes it just has to be done because there's nothing that will make a situation better. I find focusing on the healthy ones can help you heal.
Upping the vitamin E is all I can think you could do, and see if that helps. It can take a while to work. Sorry you're dealing with this with your chick.
Also recall, it could be a congenital abnormality if it's been like this from birth. If so, it may not improve. A quality of life...