Thanks a lot for a detailed reply, I really appreciate it. I'll take him to vet to get checked again as you said. Also I would try to find the wet food you recommended. Thanks againFirst, please re-read @Mamanyt1953’s Post #52 again. She explains precisely how to introduce wet food. Once he is eating wet food, he still needs dry food available 24/7 to munch between meals.
Secondly, kittens his age should not get diarrhea from KMR. Therefore, he may have coccidia, which is an intestinal parasite that is cured with Albon or Panacur or Metronidazole, and a vet must give it. He should really see a vet for the diarrhea.
But, there is a chance he is allergic to the whey in KMR, so try full fat goats milk instead for a few days. You’ll find it in the fresh dairy section of the grocery, or powdered on the aisle where the canned and boxed milk is sold.
For wet food, I suggest Fancy Feast chicken pate. No chunks, grilled, or shreds - just smooth pate. Chicken or turkey - no fish.