I would say that you're fully stocked now. IMO
, don't add anything more. You may want to consider rehoming the pleco to another tank, if you have one available. Plecos can latch on to a Discus' side to feed on the slime coat. Never seen it happen, but seem to hear a lot of stories . . . If you move the pleco, you could probably get by with a small group of cories or kuhli loaches to clean up any food that sinks to the bottom. However, if you plan to breed your discus, it would be best if they were the only fish in the tank.