Female Platy Behaving Oddly

[Skydive]

Hi, recently I purchased 3 platys from a local aquarium store. 1 is a male Blue Mickey Mouse variety (though I believe he is a hybrid with an orange hi fin because he has a large orange dorsal fin), 1 Hi Fin, and 1 Peppermint. The Mickey Mouse is a male while the other two are females. Today, the female peppermint suddenly retreated to the bottom of the tank and is hiding under a tank decoration. She appeared perfectly normal earlier, and all the other fish appear normal as well. I can't see her very well since she is hiding but as far as I can tell she doesn't look sick or anything (no popping eyes or swelling body). Is she in early stages of pregnancy? What's wrong?

 

[BeccaAmes]

I wouldn't worry too much! Sometimes fish just like to hide, whether it's because another fish is bothering her (maybe a male has been bugging her?) or they just like to be alone, and if she doesn't look sick, I don't think there's anything wrong with her. I suggest you keep an eye on her just to be safe.

 

[Skydive]

.... She's dead now.
 
I have no idea what killed her. She did eventually come out of hiding and was acting fine but then I found her dead today. I tested the water and everything checks out (NO3, NO2, NH4, pH). All the other fish appear to be fine.