hens fighting....so about 3 months ago i noticed 3-4 out of my 10 chickens had their necks plucked clean and their tails plucked clean, i figured that one of the chickens was beating up the others, but never witnessed any fighting. now just recently ive noticed 5-6 of my chickens have bald heads! this time ive seen one chicken pinning the other down and biting the feathers off the other's head! this has gotten so violent that one of my chickens is blind on one side now (her eye got pecked). i dont know what to do... i hang heads of cabbage, i through bird seed down, they even free range about 5 acres of field during most days. my pen/coop square footage is about 100 to 120 sq ft. i marked the chicken that i caught mounting the others and she has consistently been the one beating on everyone else i also noticed a couple others that have normal heads that fight with each other, they were dust bathing and got to close to each other and they puffed all of their feathers and started jumping up in the air and pecking and scratching each other. im new to chickens and am in desperate need of suggestions! the only thing i can think of is to kill her, which im fine with doing, but i want to make sure that will fix the problem before i do it. THANKS!