Our rescue pup has a very sensitive tummy. All dry food gives him the runs and some tinned food. I don't think it is allergies as he is fine with raw food and we haven't excluded any protein types. He has a good variety of protein types plus veg, offal, and bone. It could be a wheat allergy but he doesn't have any other symptoms. His eyes and ears are clear, his coat is healthy and he's not itchy.
Anyhow, I sometimes struggle to get his raw food and cannot afford to feed him tinned. I need a dry food to keep in for times when getting his raw is hard.
We have so far tried James Wellbeloved, Skinner's chicken and rice and Autarky puppy. All made him liquid shit several times a day. Some tinned foods also have the same effect eg Chappie. The tins he can eat are too expensive.