do 7 week old chicks have a pecking order??

hi when my chciks first hatched one of my leghorns had splayed legs so i removed her from the others to give it a fighting chance and i also removed my black silkie chick with it as mummy hen was atacking it and stamping on it, i assume because it was the runt of the litter as they say so i put them 2 in my house for a while them into a rabbit hutch and today ive put mummy hen back into the flock with the other hens and put the 2 separated chciks in with the other chicks in another coop well......the leghorn is fine its the biggest chick out the lot considering it was the one with splayed legs and the black sickie is getting attacked but the white silkie chicks, its screaming in pain and the leghorn comes to its resuce and they back off for a bit but then at any given oppotunity they are back on it hurting it. is this normal do they having pecking orders? if so why are they not doing it to the leghorn ive put in aswell?

ive never heard screeching like it the poor little chick, its been our favorite since hatching as it was the smallest and the only black silkie to hatch the others never hatched i have another leghorn already in with the white silkies and even that one isnt bothered by the new leghorn and they are about the same size and its not attacking the black silkie. it just seems like the white silkies are the mean ones