The pain from the stones may be what is causing him to act like something is wrong or there really can be another problem. I would have it looked at to be sure.
Lars, my 4yr male had stones last year. They put him on antibotics for the infection, but also on Hills CD. He had to eat the food for 3 mos. The stones did dissolve from the change in diet. If they had not, they would have had to operate to remove them. At the time he was also testing borderline for diabetes. Also, contributed to diet. After reading many articles on diabetes/stone related problems I was shocked at how many are caused from improper diet. Most foods are high in corn. A cat is a carnivore and should not eat veggies, let alone high sugared veggie like corn. Since feeding only meat w/low veggie/starch content he is well within normal range.
Yes, it is possible. I'd take him in to your vet if you haven't already. You may want to check out the magnesium thread on this page that just came up, coincidentally. Kitty foods/diet is a commonly misunderstood thing.