Could you also tell us some other information? The more information we have, the better we can help you.
A good list of questions that help are in the second sticky in this forum. If you could answer those into here it would really help us be more specific.
In the mean time, are they eating growing crumbles right now primarily? I see they're kept on nice clean shavings, she looks pretty well feathered. I can't tell her weight - does she feel light or thin to you?
Any signs of parasites (lice or mites) on any of the babies?
Do you have other birds nearby at all? Were these from your stock or hatchery? Can the baby bend her legs, or does she stick either of them straight out?
No access to wet or soured feed? No diarrhea? No solid feeds yet other than crumbles, yogurt, boiled egg, etc?
When you give her the stuff ivan recommended, I'd also dampen a little bit of feed and add a 1/4th teaspoon of plain yogurt. You can even give her a little boiled egg mashed with water (with a little of the yogurt) and give that to her on the end of a spoon. Add a little honey or sugar or karo syrup for some energy. If you make it thin, she can drink it and still get both nutrition and hydration. That could help her. The vitamins seem like they're going to be important. Vitamin deficiency isn't yet ruled out. I'd make sure she has some food in her before the vitamins, even if it's the boiled egg broth at least.
All of your other babies: you will want to pick them up, rule out light babies, rule out parasites, make sure they're all of really good weight. Sometimes at this age the more vigorous babies will keep the meeker babies from getting enough food often enough. Sometimes two feeders help. Other times it takes two brooders, putting the smaller one sin the second to allow them to catch up. So check them carefully, particularly their droppings. They should be normal droppings mostly with a few cecal droppings (like melted chocolate) mixed in here and there. They shouldn't be mucus in texture, shouldn't have the whites mixed in a slimey way with the feces, etc. There shouldn't be rusty color nor red bits usually.
All of the babies could and should get the yogurt, too. 1 tablespoon should give 6 babies a good dosage of living bacteria to help them in case this is something digestive. Do that weekly from week one to eight to help them thrive and feather better.
Are you feeding medicated feed, by the way? With amprolium, not BMD?
I look forward to your reply.
