You definitely don't want to just instantly stop using the buffer. The shock of sudden change is what is deadly to fish. I do not know specifically about cichlids, but the general rule of thumb is to acclimate your fish to the water quality you have instead of constantly adjusting parameters whenever possible. I would get a second opinion before you make the change (lol Deckape!), but personally I would slowly ween them off the chemicals over the course of many teenie tiny pwc's. Look at it this way...for the sake of easy math (I know they're not realistic numbers) if you had a pH in the tank of 6, and tap pH at 9... If you did a 50% pwc you would instantly have a pH swing of 1 1/2 points. That would be absolutely devastating to your little swimmers. Im sure it would be more complicated than that because there's other factors I'm not considering like alkalinity levels, dissolved solids, buffers, etc... (I'm not a chemist), but in principle that's the way I understand it.