Since your hen is feeling sluggish, give her a raw yolk with no whites once a day. It should help her to perk up. It will provide some nutritional source and protein. Don't allow the other hens to eat any of it since there doing fine.
When you have hens not laying you should offer them a high protein feed without calcium to help balance there system. Layer feed have minimal nutritional value and mainly just sustain them and keep there calcium in check for egg production.
You should consider a better quality of feed like...