Kitten and loose stools

I'm stumped.

The kitten is approx 8 weeks old now or so. I started him on canned kitten food about 5.5-6 weeks old and ttansitioned him to softened dry kitten food about a week later. He's started eating the kibble without it being softened now though since he gets canned in addition I tend to just mix the dry food with the canned.

He doesn't drink enough water so I don't want to take him off canned food. I had started him with the blue buffalo kitten canned food but my husband wants to feed him the Innova kitten canned food since it was cheaper but still better ingredients than a lot of cat foods out there. As for the dry food I have him on a blue buffalo grain free kitten dry food.

He had colitis which he was treated for and he has been dewormed, but he is still having diarrhea that just doesn't seem to go away. He isn't acting lethargic in any way and is a typical super playful ninja kitten.
Any thoughts as to why he could still be having diarrhea? The vet said that he looked great after his colitis treatment finished, but is there anything else I should have them check for? What can you give kittens to help firm their stools? I know with dogs you can give canned pumpkin but I'm at a loss when if comes to cats.

I looked online and you can give cats canned pumpkin just like you do for a dog.

Did the vet suggest staying away from any ingredients so the colitis doesn't come back? I know some people find Blue to be a very rich food.

The vet didn't suggest anything food wise though when it comes to food I usually take what vets say with a grain of salt.

What would be a better kitten food alternative? I want something better quality but that doesn't cost an arm and a leg since I'm already paying a bit to feed the dogs Fromm.

I've always weaned the tiny kittens off onto Royal Canin Baby Cat. No, I wouldn't feed it long term to a kitten, but the kibbles are the perfect size and I think it is bland enough to really help transition them over.

As for helping with the loose stool, you could try a probiotic like Benebac.

Probiotics are a great idea. You might also consider another check of his stool to rule out anything like coccidia.

My cat actually needs grains to have good stool - he had on again off again bad stool for his first 6 months until I put him on a food with grain in it and voila, good poop!