Do this after you feed them and when they get cranky. Tiny kittens need a little help from you to eliminate. Using a cotton ball to mimic the mother's tongue works well. Don't panic if a kitten fails to have a bowel movement. Each kitten is different and some do not go every day.
Diarrhea is a more common and serious problem.
At the first sign of the runs, dilute the formula just a little. If there is no improvement by the next day, see your veterinarian immediately. Kittens dehydrate very quickly. Therefore, the kittens' weight should be monitored daily. Pull the skin up.