well you just treated him a few hours ago...give it time
Thats good that you notice improvement today though. Once he does start eating again, try my trick with the chopped peas. It actually helps bring out the color in oscars too but I dont know the science behind that aspect. Oscars often suffer from malnutrition so make sure he is getting a good stable diet of pellets, frozen and vegetation. They even love small cickets too as insects are part of their natural diet. Avoid live feeder fish for as long as possible.