I'm not sure if this theory would even be realistic, but could the brahma be pecking the slw because both the brahma and buff orpington are yellow, and the slw is darker and looks so different? We still have the brahma separated and haven't tried putting her back with the others yet.
Crazy as it sounds, I have a Buff Brahma cockerels that has it in for all of my black australorp hens. I noticed this from early on. He has always pecked at / went after black chickens with vigor! I don't know why. Maybe he doesn't see them as chickens.
