Ok i have four discus in a tank. My water is perfect nothing is out of range. I do water changes every other day. I have good filtration aand airation. But, one of my discus is just hanging out at the top in the corner. He is not gulping for air, he is just staying there away from the group. His colors are pale. And i have not noticed him eating. I can't figure out what is wrong. I have noticed one of the other discus is always nipping at his fins and chasing him but, other than that nothing. Any ideas what may be wrong or what to do?