[Tracy M]

Slippery Elm Bark works great to firm up stools.

http://healthypets.mercola.com/sites/healthypets/archive/2012/03/26/dealing-with-dog-diarrhea.aspx

I also would add a digestive enzyme and probiotic to the food.
Mercola has a great one as well as well as NaturVet

http://shop.mercola.com/product/healthy-pets-digestive-enzymes,271,90,0.htm

http://www.naturvet.com/index.php?
page=shop.product_details&flypage=flypage_images.tpl&category_id=15&product_id=90&option=com_virtuemart&Itemid=8

Another option is to go completely frozen raw and see if that improves the stool.
Maybe try rabbit as a protein.