This is what I would do if these were my dogs -
1. I'd do the fecal profile including all the tests despite the costs. They are dependent on you for their well-being and I wonder how you'd feel if you had diarrhea for a month. It isn't comfortable for them - I don't say that to attack you but to impress upon you that this is not a good situation you have going for these dogs and enough already. I'd do the salmonella profile if for nothing else but as a rule out cause. Given that you feed raw, there is a higher chance of salmonella. Salmonella is the most frequently reported cause of food borne illness in humans and lately many recalls of dog foods and treats are showing contamination with salmonella.
2. I'd switch off of dog food and feed home cooked food and never go back to raw. I realize that some dog owners report their dogs do well on raw, your dogs do not seem to be in this category.
3. I'd remove any raw foods or any treats that were processed or store purchased. I'd never add them back and I'd feed fresh treats - frozen veggies thawed, fresh veggies and some fruits, etc. My dogs very rarely eat treats - I have one local bakery I buy from where I know every last ingredient going into the product, the person making it, the human grade ingredients used, and the preparation methods and cleanliness of the facility.
4. I'd add probiotics -- I keep this on hand for my dog Daisy who has multiple problems including IBD and liver shunt. One dietary indiscretion and there are loose stools. This product clears it up in 1-2 days --
Acidophilus for Dogs & Puppies, Dog Probiotic, Kosher & Lactose Free - 16 fl. oz. - Dynamic Health. I caution that I would only use a natural remedy IF AND ONLY IF AND WHEN I had ruled out ANY AND ALL bacterial or viral causes of the diarrhea by doing #1.
Good luck.