Sorry to hear. I've been learning since I got my heckel discus in and someone recommended I add roobios tea. You want to orange loose leaf type and add it in nylon bags to your filter to give it a dark tea color. It doesn't soften water but apparently it adds natural bactericides to the water along with some chemicals that help the fish relax. I used it and my discus improved after I struggled with them the first week.
I get mine on amazon. That with peat added to the aquarium should help a lot.
As for discus buffers, they are used to reconstitute RO water and actually serves to add minerals back to the water. You'll end up adding more TDS if your using it on tap. Peat acts as an ion exchange and should he the only thing you use to soften water.