I have 2 oscars and only one is having these symptoms. He swims around like normal, but his appetite has been smaller lately. His lips look swollen and he takes large breaths through his gills. It looks like he is gasping to me, but I dont know any other way to describe it. This has been going on for about 2 weeks now. He does eat, but not as much as usual. The temp in the tank goes from 72-74 and I have not tested the water. I siphoned the tank as usual about 4 days ago, and I did a 15% water change. Should I go buy some medicine?