Personally, I would do a consult with a vet nutrionist. It may very well be that home cooking could help, but I would never home cook without the advice of a vet nutritionist.
I have two pups who are currently doing very well with their medical conditions because of the advice of the vet nutritionist that I use. I cannot say enough about their advice! I have done consults in the past as well..but the two I mentioned are recent. One of them has a very serious condition, lymphangectasia, and she is doing fantastic a year after her initial diagnosis ... all thanks to her diet!
You can find one at:
American College of Veterinary Nutrition
Many of them will do consults through your vet via email or telephone.