Why is my Molly chasing my Platy?

Lately I have been noticing my Mickey Mouse Molly chasing my Red Wag Platy. The Molly doesn't appear to be aggressive or nipping at the Platy. I'm not entirely sure of their sex. I think the Molly may be female but again I'm not positive. Also I've recently been dealing with an ammonia spike (NTS) which is why the Molly is slightly burnt. They seem to be doing better since I've been taking the necessary steps to improve the water. Currently have it down from 2 ppm to 0.25 ppm. But yeah.... What's with the chasing?

 

Can you post separate pics of the molly and platy?

 

Was trying to get one of each but this single turned out pretty good...
If you need something better I can try again. It's difficult to get a great shot when they are always on the move ...

 

They’re both platies and though it’s hard to tell from the pic, both appear to be male.

 

Ah, so they are both platy. Thanks I was misinformed at the pet store! Guess I put this in the wrong forum then...

 

They’re both platies and though it’s hard to tell from the pic, both appear to be male.

I was abut to say the same thing lol. . They are both males.