I'm sorry to hear that Hank isn't feeling well. I'd also take him to the vet for a check up just to be on the safe side. Kittens can become very sick very quickly. If everything ends up being fine then in the future you can give him a little bit of canned pumpkin in his food and this will help keep his poos much firmer. I hope he gets better soon. Please continue to keep us updated about him.