The NV has a bunch of fruits and veggies. The CountryPet doesn't. I believe fruits and veggies can be difficult for cats to digest. This may be your problem. Most processed foods have them also.
If this is the case I'm surprised the probiotics didn't help....
ngredients: Chicken, Fish, Beef, Lamb, Water (sufficient for processing), Whole Eggs, a pinch or two of Vitamins and Minerals consisting of: Salt (Sodium Chloride), Choline Chloride Supplement, Magnesium Oxide, Zinc Sulphate, Ferrous Sulphate, Vitamin E Supplement, Copper Sulphate Supplement, Manganese Sulphate, Nicotinic Acid, Calcium Pantothenate, Vitamin A Acetate Supplement, Vitamin B2, Calcium Iodate, Selenium Supplement, Vitamin B12 Supplement, Vitamin B6 Hydrochloride, Vitamin B1 Hydrochloride, Vitamin D3 Supplement, Folic Acid.
NV organic Chk:
Organic Chicken, Raw Ground Organic Chicken Bone, Organic Chicken Liver, Organic Chicken Heart, Organic Chicken Eggs, Organic Bok Choy, Organic Carrots, Organic Apples, Organic Pears, Organic Persimmons, Organic Flaxseed Oil, Organic Yogurt (Organic Grade A Pasteurized Milk, Organic Nonfat Milk, Fructan, Pectin, Live and Active Yogurt Cultures: Lactobacillus acidophilus, Bifidobacterium lactis, Streptococcus thermophilus, Lactobacillus bulgaricus,
Lactobacillus casei), Organic Alfalfa Sprouts, Organic Parsley, Organic Blueberries.