You might try some muscle meat only, no bones, and just a few bites to start.

Most of my crew cannot do dry food combined with raw.....so you also might try spacing out the raw with the dry as much as you can. Let the body digest them separately.

Another thing to consider, getting a round of probiotics through him. Possibly the vaccines messed with his immune system and the balance in his gut.

Thanks I will give that a try.