Most commonly kept mbuna species (judging by your use of "africans", a pretty unspecific term, which is most commonly used for mbuna) are so far removed from their wild caught counterparts that the pH and hardness are pretty insignificant. And even then, not all areas of the rift lakes are extremely hard or high in pH. Malawi varies quite greatly from 7.7 to 8.6 anyway. I would worry less about getting the pH higher as I would keeping it stable. I have tangankyikans (including wild caught goby cichlids) in pH 7.6ish and they're doing just fine. Adding crushed coral and limestone like holey rock will help quite a bit given you use enough of it