Hello!! We are currently working on the same issue with our vizsla. Our vet had put him on Tylan and B12 injections and Science Diet z/d. The kibble really upset his symptoms to the point where he was pooping water. I had tried to "doctor'" this issue on my own and had his symptoms subside but he still couldn't gain weight. Now we are seeing an integrative holistic vet and he has improved sooooo much. Best advice I can give is find a holistic vet. Seriously has been a game changer for my boy. I feel for you so much because it's heartbreaking to watch them suffer. Please let me know if you have any questions! This forum has also been a huge help and resource for us.