My cat Cera had the same thing as a kitten and any food we gave her caused her to have the runs. I found a wonderful book called The New Natural Cat, by Anitra Frazier, it is still in print, try chapters.indigo for the best price. I used the raw-food diet recommended and it cleared it right up. We fed the cats the raw food right up until our oldest started crawling around. Then we switched gradually over to a prepared natral food and the runs haven't been back. Science diet isn't the best cat food in the world. We have the cats on it because Lucas has FUS and it needs to be controlled through diet and the SD is what's available here. If I could be sure that my kids weren't handling the food I would go back to raw again. They are still at the stage where they might test the food for the kitties. They help feed them as well.
The slippery elm is also recommended as well as chlorophyll, this can be in the form of a greens drink powder sprinkled on the food, my mom's cat liked spirulina on his food. Or there are drops available at health food stores but the powder is the most economical way to go.
Fins, Fur or Feathers I gottahavepets!