As I said in your other thread, the fin shape will only be a small hint at the final condition when fry are as young as yours are. If your fish are 4 months old, you might more easily tell a nice fan tail from a more common fish, but even then you will be going on mere hints of the fish's potential in that respect.
and if they lived on land I'm sure locusts would be jelous of not only the numbers of babies but also how much food they can put away. I've ended up having to toatally split the males and females into seperate tanks to try and slow the ever expanding