Hi ,
Baby discus do not grow very well in a planted tank. They need a lot of food and waterchange. It is impossible to keep ideal water condition in a planted tank.If you are happy with the size of 12 mths old discus being around 3 1/2 inches then its ok.
But if you want 6 inches discus then I suggest you grow them up in a bare bottom tank and put them in your planted tank when they are adults.
Key to big healthy discus is plenty of food and waterchange when they are young.
I personally won't put discus with angels. Good tankmate would be cardinals, rummynose, rams, hatchet , cory
Always quarantine new fish for at least 2 weeks. I quarantine mine for 6 weeks before mixing it with my existing fish.
Hope that help.
Cheers,
Ronnie