Ok. First off you are overstocked. Even small oscars put a huge strain on the bio load of a tank. 55 gallons is hardly enough room for one adult oscar. They say 55 is minimum for an oscar but I wouldn't do it. I keep mine in a 125 gallon with some silver dollars. I've kept many oscars and cichlids over the years and I can say that one oscar in an uncycled tank is a lot of work let alone 2 and 2 other fish. Then there is stress caused by aggression. Even though they are small there is going to be some pecking order getting worked out amongst themselves which will lead to stress. Then there is trying to get 2 oscars to get along. Unless it's a male and female, and the female accepts him as her mate, or 2 females that will tolerate each other, one will end up needing to be rehomed. Oscars are hard to get to live together. Even if they like each other the space will be too small. Water quality is not sustainable in that small tank. They like to be alone. I know right know you think "but they like each other and they swim together and stuff", trust me that will change as they mature and one will end up rehomed or dead unless you get lucky. The best thing and the only thing you should do is pick which oscar you really like and take the rest back. Sorry to be so blunt but your current setup will not work period... You will never have good water with all those fish in there with the tank uncycled. Even with a cycled tank it would only work as a temp setup. Oscars grow so fast and are very messy with the required amount of food they need and clean water with nitrates below 20 is a must. By the way I didn't mention keeping the parrots because they are an abomination and shouldn't be in the hobby.