x2 I wholeheartedly agree. Space can be an issue as well.I never put 8 week old chicks in a flock like that. They can be killed.
You expected too much of your rooster. He will keep peace between his hens, but these are babies. They are not in his group yet and he will probably not protect them from his hens.
You also didn't follow quarantine procedures and risked introducing disease into your flock.
How are you feeding babies when the hens must eat layer feed with proper calcium levels and 8 week old chicks need starter/grower feed?