That’s correct, they are too young. With wild caught no longer an option, I think this is the best size to get them. They grow to maturity in your water parameters. Also, with mature fish you have no way of knowing their true age or their general inclination to breed. Nobody is going to sell the males and females that are currently breeding for them. Buying them young keeps everyone honest. Then you raise them and hope you get a good ratio and that you have figured out the best way to keep them happy (you will have the time).
This is assuming you want to breed them. If not…probably doesn’t matter. They all look good and they live a long time.