I bought an oscar about two weeks ago, at around 2.5". he started off fine in my tank and was eating/acting fine. Now he hasnt eaten anything (blood worms nor beef heart) in three days and barely if at all leaves his big plant he hides in. He is not out and about, looks almost depressed and just sits there not reacting to anything. I did a 25% water change and nothing. The dithers in the tank (platys and danios) are perfectly fine. What can I do? What is wrong with him? TIA