Frontosa's are able to breed even at 4" some of the females have had their growth stunted so that's why they're size are like that. I can even show you the fry they produced 2 months ago..
If you could post pics that would be great, but having kept Fronts for many years my wild caughts were the only ones mature enough to breed at that size not tank raised, and you can tell by the mooning they are tank raised. But they are cute!