The challenge I see with your fish is the lack of sufficient water changes. As a result, their growth is far below optimal. Both blue discus in picture 3 are showing signs of stunting, with the eye to body ratio much bigger than what should be. The key to growth is simply large, frequent water changes. Filtration is not a substitute.
Bullying is not a significant problem with 11 fish. These are cichlids and they will always establish a pecking order. Aggression by the alpha is spread out over 10 fish and is anticipated. Feed on both sides of the tank and everyone will get to eat. To see what Stendkers can do with sufficient water changes, see Flachens at http://forum.simplydiscus.com/showth...Back-to-Basics. I received these four months ago at 8 cm. Note the proper eye to body ratio with proper growth.