Can Platies change genders?

So I got a Tiger Mickey Mouse platy a day after mothers day I was certain was female , now it is a male? And Since we already have one male they're fighting over the remaining female. Its stressful, because I had two female fish, and now i have 2 male fish. Is there something that could've triggered this? I know it was female before, also. We used to have a white female platy that had died (we had the tiger one at this time as well) maybe that could've caused the change? I don't see why it would but I know I had a female which is now a male... has this happened to anyone else?