Is My Mickey Mouse Platy Pregnant? Please answer?

Ok, so about 6 weeks ago i baught about 12 fish at pets mart, so far 7 have died, but along next to all the ones i bought was a Mickey Mouse Platy and a Starburst Platy- The Starburst died. I didnt know the sex's and dont know how to tell? Can they receive eachother pregnant? My still living Mickey has gotten somewhat fat, but not too big,i dont see a gravid spot (do they get them?) and in that is some kind of see through pouch, that is peach colored at the anus within the fish and what looks approaching to be about 4 black dots inside. (possibly frys eyes?) I dont know hot to tell if she is or how far along she is? What do i do to prepare whether she is, please answer ALL! QUEASTIONS! PLEAE HELP.
Answers:    Many livebearers can store sperm. Sometimes they can have 3 broods with out a male present. Many of the diffrent variety can interbreed to create a hybrid. They can even breed with other livebearers from the same family. i.e endlers and guppies, swordtails and platys. Im not certain how big your tank is, what kind of filtration, and how long its been running, but introducing 12 fish at once could enjoy ruined your water quality which is why you had such a illustrious mortality rate. Most livebearers drop every 4 to 6 weeks.

check this out to sex them
http://www.fishforums.net/index.php?show...
I don't know Sorry
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