My black moor was swimming weird today and started floating to the top and going upside down while trying to swim down. I changed the water a couple days ago and pH levels and stuff are fine. The other fish are fine. They are having no trouble. Mahdi, the black moor, seems to be gasping and once in a while her body jerks a bit like she is hiccoughing. I have her separated and held in a net to help her stay upright. I've used the only medication the store near me has, Melafix. Her scales are fine and slimy, and her eyes are normal. Not sure what's wrong.