I'm a vet, did heaps of rescue kittens for a while, science diet kitten dry seemed to help a large number white loose stools, apart from standard worming all items benefit from being treated for coccidia, since combing those approaches I've had much better succes with them and less gut issues. The pig coccidia meds are the best, bayocox, 0.4ml/kg oral once daily for 3 days, repeat single dose in 1 week. If I got them before dia just a single dose seemed enough, but after a full course as above. It's across the counter but the bottle is relatively big, many vets will downpack u some. Take a stool sample to vet with u.