Picture of my hen
Featured Stories on BackYard Chickens
It looks like feather picking which can be a result of eating less than 16% protein in a balanced feed, too little room, or boredom especially if they aren't going outside to free range. I would get a tube of Nustock, a pine oil and sulfur mixture than can help the red skin to heal and prevent pecking. Watch your flock to spot any bullies, and check your feed label.