Found it great.
Responding to the last comment of Sylvester017 , you said you separated the calm chick. Think it should be the other way around, isolating the aggressive chick - they are social birds, don't like to be alone. So that'll calm them down a bit. Also by staying out from the brooder he'll lose the territorial advantage and when coming back in the other "home" chicks will have a tendency to protect their territory.
Responding to the last comment of Sylvester017 , you said you separated the calm chick. Think it should be the other way around, isolating the aggressive chick - they are social birds, don't like to be alone. So that'll calm them down a bit. Also by staying out from the brooder he'll lose the territorial advantage and when coming back in the other "home" chicks will have a tendency to protect their territory.