First of all,....are they domesticated or wild discus. If they are wilds, are we talking abouth brown/blue, greens or heckels?
In case of domesticated discus,.....I keep mine in straight tap water at PH=8 and GH=9 and I even breed them in my tap water. PH is one thing but how abouth your GH? If the water is indeed soft it will be easier to keep the discus in straight tap water. Just try and gradually add less buffer with every water changes and see how they respond. A happy discus is bright colored one with a light base color.
In case of domesticated discus,.....I keep mine in straight tap water at PH=8 and GH=9 and I even breed them in my tap water. PH is one thing but how abouth your GH? If the water is indeed soft it will be easier to keep the discus in straight tap water. Just try and gradually add less buffer with every water changes and see how they respond. A happy discus is bright colored one with a light base color.