Mbuna are harem fish, so would you want 1 male to 4 Females otherwise you'll see aggression to the weaker less dominant fish. Auratus and Kenyi
are extremely aggressive fish and you would want more than a 1m4f ratio, probably near 1M 6F. This way the male when he gets into spawning mode, will take his aggression out on several females and not beat on one and kill her.
They can also quite easily take over half of a 55 Gallon tank and will defend it extremely aggressively.
You want to really aim for 3 species of about 12-15 fish maximum in a 55g.
You have a very aggressive stock list there and I hate to say it but it will cause major problems in a 55G which WILL result in a lot of dead fish.
Yellow Labs and Red Zebra
will crossbreed, so if you want to keep them, DO NOT sell, giveaway, trade any of the fry, they will all be hybrids.
Here is a stock list that would be more suited to a 55g tank.
Metriaclima estherae Pseudotropheus saulosi Pseudotropheus
sp. "Acei" Labidochromis caeruleus Iodotropheus sprengerae
Max of 12-15 fish spread over 3 species. (More if they are juveniles until they are old enough to sex), This will allow 1M 4F ratios to be established.