I'll try to skip melafix for now...just by reading more into it, it seems to treat bacterial infection which can happen during stress and suffocation (metbaolism went down, the fish are prone to catch becaterial infection) but I think, relieving the stress and increase Oxygenation will helps them first.
If this don't help in 2-3 days, then I'll transfer him to a hospital tank with melafix.
stan