I'm currently fighting Ich in a livebearer/syno tank, using...
Slightly raised temp (26/27C instead of normal 22/23C)
Full dose Waterlife's Protozin
0.25g/l of Caorse Sea Salt today, adding another dose tomorrow afternoon (to help fish get used to extra minerals)
Spraybar of my filter (~1200lph true turnover) fully above the water surface (so tank is reduced to ~100l from 140l)
However, I don't know if Malawis need specific treatment. I suspect they will be very tolerant of salt, but I suspect they may not be very tolerant of a temp >30C (often used to try and kill the free swimming Ich form outright).