I had a sail fin molly, a balloon molly, and a red wag tail platy all together in a tank and then decided to add in what I think is a calico or tiger platy. Within a few days there were about 14 babies in the tank! I assumed they were either from the red wag tail platy and the tiger/calico platy mating (though I don't know if there was enough time for this...how long do platys need to be pregnant for before they can give birth?) or that maybe the new platy was pregnant when I bought her. Around a month or so later there was another batch of fry, which made me think it was more likely that she was mating with one of the fish in the tank (although I think they can store sperm...?). The older babies are now getting on to 2-3 cm and here is what I don't get...half are definitely balloon mollies and half are platys (some sunburst tux platys and some calico or tiger platys)! The balloon mollies are a similar coloring. I didn't even think they could breed, but if they could I just assumed you would get cross bred fish, not half and half!
Sorry for the small novel, didn't want to leave any details out. Can someone explain the most likely mating scenario for this?