It should be formed poop from eating wet food, so the kittens may need worming or treatment for parasites. You should call the vet.
After researching what holistic-minded vets say about using Coconut for pets, then after using it with my family . . . I've used it on our dogs & cats with only good effects, as long (as I don't give too much at a time, which can cause diarrhea). I share the following information about using Coconut for pets by 2 of my favorite vets, for others to learn from too.. . . It is important to remember that much of what you find on the web is unverified, and some may be actually harmful. \Make sure you confirm anything you want to do with your vet or someone you trust who is experienced.
"Probiotics: The Single Greatest Thing You Can Do to Enhance Your Pet’s Health"\ Make sure you confirm anything you want to do with your vet or someone you trust who is experienced.