dj is right - you are better off to stick to a larger group of Tropheus. They can get quite aggressive- the larger the group, the more dispersed the aggression is.
Also, tropheus are mainly to be fed a low protein, high vegetable based diet, consisting of spirulina, veggie flakes etc. If you feed them too much protein they can develop "bloat" - your other fish I beliieve like higher protein diets (not sure - been a while since I've kept Malawi cichlids)
so there are dietary differences on the fish you are keeping together. You can see if your other fish will respond to a veggie based diet, also you can feed New Life Spectrum cichlid pellets - all the fish seem to like that, and I haven't had a problem with giving it to my colony of tropheus bemba.
Tropheus are great fish to keep, I hope it goes well for you!