Identifying Molly Fry

Groovysunflowers

I have 3 fry right now, 1 black molly baby from my black molly and 2 gold dust babies from a gold dust mother who recently passed away :(

The black molly baby's mother is a sailfin Lyretail and the baby has been growing at normal rate, looks and acts healthy, thin and sleek looking. However, the gold dust babies' mother was also a sailfin Lyretail, but these babies have been growing at twice the rate of the Black molly baby. They are only 2-3 weeks old and already about the same size, if not bigger, than the 1 month old black molly baby. The 2 gold dusts also seem to be showing a pouch-looking belly...Is this an identifying sign of Balloon Molly babies?! I don't know what the father was but they were not in a tank with balloon mollies; shipped together might be a diff story. If anyone has ever had balloon molly fry or successfully grown molly fry, should this be a concern about bloating or an identifying quality?