Like I said earlier..the other chicks are attracted to the red/orange bump, they will peck at it. It isn't because they don't like the chick at this young age. Once it's dropped off, or the fluff fills in over it, they will leave it alone. Doing the right thing putting chick in with the others for a bit so they know it. Keeping them apart for awhile will cause them to see it differently. Good luck. Time is all they need.Probably because they've never been with the chick at the beginning, which is an issue. I never separated my chick from the group.
Well at least you tried.