When you purchase a breeder male in mid season, there is a good chance he has already been bred. Your pastel male who is refusing food may still be in breeding mode, thus the lack of interest in food. Co dom males often get dumped after they have bred other co dom morphs, since the breeder is planning to replace him with one on the double co dom offspring anyways. I'd put him in a clean bin free of the scent of females until he goes back on feed.