I don't think that you should put shellies in with Malawi cichlids. I also feel that a 29g is too small for peacocks.
You should make a choice of which you like better, the shellies or the peacocks.
If you want the peacocks more, put in 3 with a pleco nothing else.
If you want the shellies, get a species of shellie and you can also add one the the smaller Tanganyikan rock dwellers.