Royal Canin has Gastrointestinal kibble and canned. It does the job - both varieties have high caloric value so dog can get nutrition without overloading his tummy and intestines. For Roki RC canned ise the best when he has diarea or very loose stool. When it stops, he gets RC GI kibble in the morning and one homecooked meal. You can mix GI canned and kibble. Our vet says that in extreme cases (and Django surely is one) you have to feed only GI vet diet such as RC or Hill's, but you can mix canned and kibble if dog has bad appetite. Maybe you can start with canned! RC GI canned it very tasty and smelling so nice and meaty. But it is definitely more expensive than kibble.
Look at this
It is quite expensive, but I know one dog that had bad bloody colitis for years and recovered from it just taking Pro-kolin-enterogenic and GI food. It is british product, but I think you can get it in US.
Have you tested for parasites, especially giardia and cryptosporidia? Roki had on and off diarea, loose stools, bad appetite... Month ago I just collected his poop and took it to the vet. He came positive for both bugs. Those can wreck dog's GI tract, especially when their immunity is compromised!
We did two rounds of Panacur (first round 5 days, two weeks pause and second round three days), large doses of probiotics, 250 mg MSM and one drop of black walnut tincture in drinking water. Final test came back negative for parasites. His loose stools and anorexia are gone, his energy levels increased, his skin and coat are improving dramatically, no more gunk from eyes...
Thing is that those bad guys are extremely hard to catch. We had like six or seven false negatives. In the meantime dog can suffer for years and those bugs are given chance to wreck his GI tract. Some vets watch for symptoms ( stinky poop with lot od moucous, an and off diarea or loose stools, bad appetite) and routinely give two rounds of Panacur.