I bought 2 Clown Loaches atthe same time, out of the same tank. They were both about the same size, one of them is doing very well and nice and healthy, and the other is just getting skinny. When i feed them, he eats like its his first time seeing food! He is getting skinier......and his gils appear to have a different color. Almost a redish grey color. He's active, just as active as the rest, he's just getting skinnier and skinnier. Any ideas???????????