Chick Pulling Others' Feathers

[User4477]

Hello,
I've been introducing my 5-week-old chicks to their new coop/run outside from their indoor brooder for the past week or so, taking them out there during the day, but recently one of my chicks has started pulling out feathers and pecking at 2 of the other chicks and she won't stop. One of the chicks even has a back injury from it. I'm not sure how to go about this, I've separated the pecker from the others and gave her food alone to see if it helped (they have food available 24/7) but it didn't.

She eats the feathers afterwards so I'm not sure if it has anything to do with nutritional deficiencies. I only feed them Dumor Chick Starter/grower 20%, no treats or anything.

(The pecker also has a funny-sweet odor to her, she's had it since she was 2 weeks old and it hasn't gone away. She's the only one with that smell so I'm not sure if that has anything to do with it. She eats and drinks water normally, however.)

 

[Wyorp Rock]

Photos of the chicks, brooder, poop?

 

[Chickassan]

Feather eating is either a protein deficiency, boredom,or you've just got a jerk in the bunch.
The first two can be at least semi managed with "treats" live insects like mealworms, nice protein rich things that give chase.