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.

[emc7]

How big is your tank? You can feed the cory just befor lights out, the platies will go to sleep and cory will keep eating.

[ron v]

All cories should be in groups. You need to purchase at least three more. Your panda will be much happier.