Baby chick not growing

[DolceVita]

Hey I have bantam Cochins and one is much smaller than the rest. I would say they are 3 weeks? What can I do to improve growth. I’ve had them on vitamins for a week now and hand feed her a vitamin E pill every day

 

[M-H-Fielding]

Awww, so cute! Not sure why it isn't growing. Has it been eating?