My first step would be to try a kibble that has a different protein than you are currently feeding. My late dog got diarrhea from anything made with salmon even though he wasn't ALLERGIC allergic to it. It's pretty common for dogs to have a sensitivity or allergy to chicken, which is one of the most common kibble ingredients. You might consider a kibble specifically formulated for "sensitive stomachs" or the like. I would also have a vet do a fecal test to see whether your pup might have something like giardia or another parasite that is affecting his digestion. Also, how is the dog's weight? If he's is not lean, you may be feeding him too much, and overfeeding can cause soft stools as well. How many times per day do you feed him? If it's only once, splitting up his food into multiple smaller meals might help.
Please note that the diet "stbob" is promoting is not a balanced diet and is not advisable for long-term consumption, especially for a young dog that is still growing.