Why My Female Platy Always Chase Other Platy

[fishshl]

I bought a female red tag tail platy two days ago.
And this evening, I bought one male red tag tail platy and two female sunset corel dwarf platies.
But my first female red tag tail platy always chase the three new platies.

Is this normal ? Will they be peaceful after several days?

I also found one small female sunset platy chased my panda cory. And all platies compete with my panda cory for their shrimp pellets. My panda cory looks quite stress.

 

[Annastasia]

Give them some time to settle in, she might feel she needs to defend her territory. What size tank are they in?

Panda Cories should be in schools. This will cut down on the stress for them. Also, feed them shrimp pellets after the lights are out, so the Platies can't see it and go for it as easily.