You are doing the best you can to maintain the best possible water quality for your discus, well done. I have to admit I'm not very hot on discus I see in fish stores but these ones you have are unlike anything that I've seen. The colors are amazing and their shape appears slightly different compared to the tank bred ones.
I've got a relatively big tank 200 US gal, 2 meters long) but don't have the capabilities to keep discus. Water is too expensive here and does require RO because it's hard and alkaline (tap has a pH of 7.5, GH 14, KH 10) but I manage to bring it down to 6.5, 8 and 1 respectively with peat. Problem with peat as I'm sure you know is that it's unstable and must be cycled every 3-4 weeks.
Again, beautiful fishes well done to you