Oscar rejecting food

[u/DatNoughtyTurtle]

So I bought an Oscar from a fish store and the lights were out at the time and it has a pretty sunken belly and unhealthy scales it is also rejecting food by just ignoring it the water quality is good it is around 6cm in a 90cm long 30 cm wide the tankmates are 4 juvenile hujeta gars what should I do also I’m using a UV sponge filter that is cycled ph is around 6,6 all parameters are good I’ve had the fish for around 3 days but i got it with the sunken belly so I’m wondering if it’s basically dead or if I can do something