I've just been catching up now, learning about Madison's condition. I have sent you via PM Mango's diet. She was have severe gastro-intestinal issues a few weeks back. Even her Vet seemed out of ideas as to how to stop the profuse vomiting she was experiencing. I had a consultation with an amazing nutritionist, Susan Davis, and the diet she put Mango on has done wonders for her. I hope it helps Madison too. I know you have had Madison on a version of it given to you by Wylie's Mom, Anne, but I want to make sure you have ALL the ingredients; I think it is important.
Hope he continues to improve. I am so glad for you that the Vet bills were manageable!
Lauren
Edit: a little bit of canned pumpkin also does wonders for the tummy - I see that someone else mentioned this - it really helps!