I have a question about pecking order/bullying 🐔

Sooooo I started out back in October with my first 5 chicks
I then introduced 3 more 1-2 month olds after a few months
Then 4 more after a while
And I just last week introduced the last 12 chicks (1-2 month olds)

My question is… is it normal for the last 4 (assuming bottom of pecking order) to be absolute complete bullies to the new chicks? The older hens don’t seem to mind them as much, but the last group of 4 has been absolutely terrible. Is it because they’re at the “bottom”? Is there a way to help the dynamic?