Or your misinterpreting their behavior, as stressed fish will also huddle in the corner together. I don't know which it is but your tank is too small for the fish you have in it.
You need a bigger tank, a 37 will not hold those fish. Your Parrot may be small now but I have 2 and they are both about 6'' and they are tall and bulky they , need alot of room... And as far as your other fish, one of them would be ok in that tank.
lol you offered me the same fish, i thought you were looking for a good home do you realize he has a 37 gallon aquarium with too many fish and you want to throw an oscar in the mix?