Brown leghorn chick pulling feathers
So you are actually seeing the chick physically grasp and pull his fuzz/feathers? Is he targeting baby fuzz or newly formed/ing feathers? When he plucks, what is he doing with what he has pulled - spitting it out, swallowing it, etc?
You have quite an age range there - which can sometimes make it difficult to maintain an atmosphere that fits the needs of all involved, so knowing a bit more about your brooder may help identify if there are issues on that front. You have eight birds total, correct? What are the dimensions of your brooder? What are you using for a heat source for the chicks (some are more problematic when it comes to mixed ages and their needs)?
The photo seems a little off in color (perhaps a heat lamp is casting a red tone?) - but the exposed skin does not look like it is particularly red, irritated, etc - is that the case or is the skin showing signs of issues?
The brooder is a hamster cage 17x29 inches, with a red heat lamp in my living room. I've been watching them carefully for signs that they are too hot and they all seem comfortable. They aren't avoiding the lamp or panting and they sleep sort of in the middle of the cage usually cuddled up or on the roosting bar under the lamp. I tried turning it off one day before I got the little ones and found them all huddled and cold a few hours later.
I do have a larger dog crate I could move them to if theyou need more space. Which I was thinking of doing as they get bigger anyway before going out to the coop. And yes. A total of 8 birds.