http://www.homevet.com/petcare/docum...veranddiet.pdf
This is incredibly helpful. I know there's a lot of medical info in here, but it's so informative for those who have dogs with liver disease. Give a copy of this to your vet. It was written by Dr. Center is one of the leading experts in liver disease.
Since your dogs are symptomatic, I think it's imperative that you get them off of any diet that may contain animal proteins...They produce the most amount of ammonia and in a dog with a compromised liver, the ammonia builds up and enters the bloodstream causing more and more severe symptoms and damage over time.
Are they on prescription diets or are you homecooking?