If you're lucky you might find the vitamins in the store, which should help. I wouldn't worry too much, though. So long as your kids are kept well-fed their health bars should improve.

BTW, the baby boost is only to increase the likelihood of the mother and father having babies, so that wouldn't do much good, even if you could afford it.

If they don't improve after a few hours it might be worthwhile getting a doctor's diagnosis (provided you can afford it).