Hi Wendy,
I'm not sure about the food because I have never used this type. I would usually say fast but as it has been going on for a few weeks I would be more inclined to suggest could the food be made too sloppy for him or is there too much.
If you don't use raw chicken wings then give him one or 2 or these after his meal (you'll have to reduce the amount of meal you give him slightly) Bones are great for firming things up.
