Platty fish sick/pregnant?

[Mary]

I just got 2 platty tuxedo fish from Petco yesterday. I am not sure if they male or female but the anal fin seems to be open like a fan so I suspect they are females.
I put them in an aquarium along with my betta fish, but soon I realized betta was chasing after them (even though the guy at the store said it shouldn't be a problem) so I divided the aquarium in half, betta on one side and the 2 platties in the other.
This guy i am worried about (has an orange coat) has not eaten, the other platty (yellow) ate yesterday, but not today.

Up until 2 hours ago all 3 fishes were fine, but then I realized the orange platty was staying on the bottom a lot, she was opening her mouth a lot (kind of like trying to breathe) and then she started to lose balance and was laying on the side a lot.
So I removed it from the aquarium put her in a separate container with the same water conditioner, in case she has some disease to not spread it to the other 2. She is not moving, staying on her side, her gills are moving though. She actually seems fat, but I am not spotting a dark spot to think she is pregnant.

Please help This is my first time with Platties.

Are these signs of possible pregnancy?
Do you think she is just stressed? Or has some infection?
HELP I think she is going to die

 

[Sunshine]

My best guess would be that she is stressed from the transition,i think being chased by your betta could have put additional stress on her,when they start tipping to the side,i think it is possibly to late.

Did you follow direction how to integrate your fish into the new tank? If so I think it was just the stress of the transition,if she is really blowed up without her being pregant,this could be a disease.

Sorry
hope your fish will make it.