It sounds like you started off with discus without having your tank fully cycled. As stated, we can help you IF you will test your water and report back the readings for.
ammonia:
nitrite:
nitrate:
Temperature....
Now I know you have read up on discus, because you are using RO water and such, but most of the time unless you are breeding the ph doesn't matter IF you use care in acclimating your new fish.
As for KH and GH, I feel messing around with these can cause HUGE problems for a beginner, and beyond most peoples abilities at first to keep stable, this is the key, and fluctuations can cause disaster.
My understanding of discus is that they need pristine water conditions, and the first and best thing you can do for them would be numerous water changes.
I'll comment more after we know what your water parameters are.