can female platies curl their fin and look similar to males?

[Hummingguppy]

Help! I just went to the petstore to buy three platies, 1 male and 2 females. But they all had a pointed anal fins! I asked the store and they said they had not ordered males in particular, so stumped, I only bout one that I though was a male, and went home. Then after a few hours of swimming around in my much roomier aquarium, 'his' anal fin spread out and looks like a girl! Was he/she stressed in the previous aquarium? Help!

 

[henningc]

Platy sexing

I have seen late bloomers do exactly that but in reverse. If the anal fin is pointy than you got a late bloomer.