Is the light on 24 hours? I've heard that some aggression can be due to no dark period, too. You might try to give them more hiding spots and more space. You can also make a cave out of a heating pad, instead of a light for warmth. Might make things more peaceful. These threads have a lot of great ideas.
https://www.backyardchickens.com/a/yes-you-certainly-can-brood-chicks-outdoors
https://www.backyardchickens.com/t/956958/mama-heating-pad-in-the-brooder-picture-heavy-update
https://www.backyardchickens.com/a/yes-you-certainly-can-brood-chicks-outdoors
https://www.backyardchickens.com/t/956958/mama-heating-pad-in-the-brooder-picture-heavy-update