Just an update. Elliot's ears weren't getting any better so the vet decided to put him under to clean them out properly. He got a 2cm wad of goo out of the bad one! We are now doing ear drops, an ab and pred. I'm in the process of changing his diet to the Acana 70:30 fish food as its low in carbs and a novel protein. I also have a wet fish food as he won't eat plain dry, but the ingredients don't have percentages and it has some potato/vegetables so I'm not sure about it from the yeast point of view. He's also getting ACV. I really, really hope this works!