I had 5 silkie chicks together and the two that started fighting like yours turned out to be roosters. I kept them separate and every time they got together feathers would fly. One day I was tired of seeing the one rooster have to live in solitude and feed him separate so I let him out, walked away and let them do their thing. When I came back the next day it was sorted and one was the dominate roo and the other one showed him respect so I assume he got his butt whipped. They ended up living together in a run away from hens with no more problems.