We had a similar situation in our colony recently. Nice litter of eight, all doing well, and then MidnightCoder noticed a kit with a bad eye, 4-5 weeks old. He brought it up to the house and we found it was very thin. I figured that it just could not compete for feed and we installed it in a cage in the kitchen with alfalfa hay, oatmeal mush and water. It ate a good amount in the first 24 hours or so. Poops were normal. We brought up one of its siblings for company, hoping to make it feel more comfortable in strange surroundings. A couple of days later it went downhill fast. We were on the point of culling it when it died. I concluded that the eye infection had gone systemic but that is only a guess.
Kits raised on a natural diet do grow more slowly, even if given free choice alfalfa hay. But in general there are no problems with weaning enteritis and so losses are few. Here, natural feeding is far less expensive than pellet feeding, so I can afford to grow them out a few weeks longer. I've never had a problem with feeding alfalfa hay to rabbits of any age. They also get some grass hay (mainly for nesting), whole grain and as much fresh food as the season allows. And a trace mineral salt block, of course.
Kits raised on a natural diet do grow more slowly, even if given free choice alfalfa hay. But in general there are no problems with weaning enteritis and so losses are few. Here, natural feeding is far less expensive than pellet feeding, so I can afford to grow them out a few weeks longer. I've never had a problem with feeding alfalfa hay to rabbits of any age. They also get some grass hay (mainly for nesting), whole grain and as much fresh food as the season allows. And a trace mineral salt block, of course.