mblue and melafix will not do anything for him since he doesn't have any open sores or wounds...
The best thing you can do at this point is to give him calm in the tank. Keep the lights out, see if you can keep other fish from picking on him (without putting him in a net or seperate tank, this will just stress him out more), if he recovers great, if not, at least he died in peace. Water changes always seem to help, so if you can do one of those without really disturbing him, I'd try that too.