Guppies chasing my platy

I have 4 male guppies. and 3 platys, 2 female 1 male. And I've noticed my guppies chasing the male platy all around the tank. Why are they doing this? And what should I do?

 

What size is your tank? It could just be playing, if you see nips or bites than I would isolate the bully fish

 

Yes, what size tank?

 

It's only a 10 gallon tank, I plan on upgrading soon. But could that really be the problem? I have plenty of hiding places and plant cover.

 

Yes, that's the problem. What are the genders of all of the fish, including the guppies?

 

All the guppies are male and I have one male and two female platys. But the guppies only chase the male platy.

 

Sounds like they're jealous.
Even though they can't interbreed with each other, they still may try.
You need to have livebearers in a ratio of 3 females to every male.

 

My guppies chase my platys all the time. they constantly try to breed with the females. even though they can't, they sure try.