I see, but it's been 2 weeks since the fight correct? He's not getting better.
While it could be related injury, by 2wks I would expect to see improvement. Possibly he was injured and the stress from the fight/injury caused him to become symptomatic from an underlying disease like Marek's...
Can you post some photos or upload a video of him to youtube, the provide us a link.
I'm sorry to hear about your rooster, I'm sure it's very upsetting:hugs
You mention that you have given him a mix of different vitamins - what exactly have you been giving him - got a photo of the product(s)...