I just saw these nice wilds now. Just wanted to suggest to you:
Do not keep all 3 species together. Definitely Heckel Discus comes from a complete different habitat and environment and extreme water parameters - those you should definitely keep for them selfs if you want to appreciate their real beauty and for them to stay healthy.
The Green Discus (S.. aequifasciatus come also from very different waters than the Browns.
This is my suggestion from one who has colelcted and studyied them all his life... (or betetr 10 lifes).