You have a couple options, but without knowing the size of your tank or what else is in there I can only give you some suggestions.
With platies, you can tell male vs female by the bottom fins - females will have wider fins and males will have more of a rod-like fin. Unfortunately this only works with fully adult platies, as it can be hard to determine with young platies.
If you have enough room, you can get 2 more female platies to add to even them out. This obviously is only an option if you have enough room to add 2 more fish. Otherwise, you may have to get rid of one of the males - IF you are sure one of the females is actually a male. It might be too soon to tell, and sometimes platies are funny. It could just be a boisterous female, in which case the male is getting a taste of his own medicine for a while. Wait until mating time, then you'll really be able to see who the males are.