Bought 2 male guppy for my tank… gone wrong

Hello everyone I am posting because I require some advice. On Sunday, I bought two guppy’s to go into my Platy tank which has been cycled for a few weeks now. No deaths or sicknesses have occurred until I noticed one of my guppys was not moving yesterday but was swill moving its tiny little fins in the front. I went to eat dinner and I come back and I can’t find it. I picked up the decoration it came out started swimming upside down and promptly return back to its hiding. The other guppy, male, has been trying to what seems like mate with my other three female Platys as they swim away. My question is if the Platys will get stressed by this guppy trying to mate with them and wether or not I should return him along with the crazy seemingly sick fish. Any advice would be great.

 

The platys should be fine, though I do believe that platys and guppies can breed and have hybrid with deformities. I definitely would return the crazy guppy.. I'd hate for him to be sick or something's and affect the others. It's up to you if you want to return the other guppy.
Edit: swimming upside down is a symptom of swim bladder disease

 

Don't worry guppies and platies wont cross breed. Swordtails x platies have been bred for decades and mollies x guppies, more rarely but still possible.

 

Don't worry guppies and platies wont cross breed. Swordtails x platies have been bred for decades and mollies x guppies, more rarely but still possible.

That wasn’t my fear but anyways as of yesterday, the guppy which I suspected to die, has died, it was late at night when I checked so I did a water test and went off to bed. Ammonia was at.25
But earlier in the day I had doses prime in advance so I went to sleep. Right now I’m going to go forward with a 3-5 gallon water change and I’m returning the other guppy as I think I will go back to platies. Can I buy another Platy today or should I wait.

 

Hi
Sorry there weren't any responses.
Are the rest of your fish still ok?

I'd hold off buying anything since you're not sure why the new guppy died. Make sure they didn't carry anything in with them.