1 of my corys is acting strange. it perches on the leaves of plants, and is a liitle darker in complexion and skinnier than his tankmate cory. I know that i feed them enough. It is breathing kid of shallow. It doesn't have any other visible symptoms. Ammonia, nitrite good. Ph 6.8-7.2. And hardness and nitrate good. I have a hospital tank, aquarium salt, and some medicine i can use if needbe. Please respond soon, so i can treat it if necessary. Thanks.