Omg @aart I love this problem chick separator.Don't bother with the blukote, can actually attract pecking from other birds,
and over-preening from the bird it's on.
Separate the pecker(see pics below).
How old are these chicks and what is your brooder like?
What all and how exactly are you feeding?
How are you heating them?
Pics would be of great assistance.
I use this in the brooder to confine a 'problem' chick.
Made of 1/2" hardware cloth:
View attachment 1703467
Or you can just make a 'corral'(lower right) out of the same HC.
View attachment 1703471