What size tank are you keeping them in? Many cichlids release an "anti growth" hormone in a tank to keep them from getting too big in an environment. I hope I'm eplaining this right. I had a yellow lab in a small tank for a while and he stopped growing but once he was in a larger tank he got way bigger.
As for size my yellow lab Nemo is about 4 inches long. I don't know about Keynii they are always so tiny and cute at my lfs
. My mol. gen. prof has had a cichlid for 5 years and he's still going strong.