There are just to many nice discus in the world today to keep ones that are not nice. Go ahead and cull them and save your limited tank space for nice fish. Nothing in this old world is guaranteed a long life. In the wild animals with issues are the first to go. Why should mother natures law be broken just because we have the fish in a tank? Just because we have protected them from preditors does not mean we should keep them. It means that we need to take the place of the preditors and weed out the small, weak, deformed fish.
-john