I sent an email to the vet nutritionist. She answered me this morning and is going to work on something for Giz...he is not going to be able to eat the SO anymore. I don't know for a fact it had anything to do with it, but he really does for sure need lower fat in his diet. I should have contacted her when he had problems with the home cooked diet instead of just putting him back on the SO. Worked for months...but I am suspicious that it might not have been helpful here.
Poor Giz.