Could be a hybrid or just an extremely overfed and therefore abnormaly large specimen. Most Mbuna grow unnaturally large when fed too much.
And with Mbuna it's always difficult if you don't know the source. The market in many countries is flooded with hybrids.
That's an quarantine tank... they're in a 125 gallon now.Mind me asking what size that tank is? It looks really small to be housing adult Mbuna.