The tank is large enough for 3 oscars. But, as with people, sometimes 3 can be a crowd. Your fish may live peacefully together for years. Or, 2 may form a pair and harass the 3rd. Just keep an eye on them, watch for any aggression, and if it becomes a problem, be prepared to rehome the "odd fish out."
How many Pictus catfish do you have in the tank? Pictus prefer to be in small groups, so if you have only the one, you may want to think about picking up 3 more or so.