I had a cat who had a "sensitive stomach" beginning as a kitten. My vet told me that the dry kitten chow I was feeding him had a high corn content and could irritate his stomach. He suggested switching to chicken baby food mixed with rice cereal for babies briefly until the diarrhea ended, then changing the kitten food to another brand. This worked and for the rest of his life, he had to eat dry food for cats with sensitive stomachs.

I don't know if this is the problem with your little tyke, but that was the problem with mine.