These cats and kittens need to be examined by a veterinarian. Intestinal parasites, dietary indiscretion, infectious disease, giardia, abrupt food change, and toxicity are all things that can lead to mass outbreaks of diarrhea. Your veterinarian will run tests to determine the cause of the diarrhea. I am concerned that the kittens are becoming dehydrated. Kittens are very sensitive to dehydration, hypothermia, and hypoglycemia (low blood sugar). Even mild illnesses can become very serious very quickly in kittens due to these secondary complications.
I have one question have you feed them with milk because cats and kitten can have diarrhea if you feed them to much milk if you haven't been feeding them with milk then take them to the vet as soon as you can!From:(The Cat Expert)