
Hi shannon
there is no all round "best food" for a dog with allergies or intolerances other than any food which does not contain the ingredient/s to which the dog's system reacts. If a dog is allergic to chicken then pointless feeding it regardless of "how good the brand" and/or other ingredients, % of this, that and the other. However successful with dogs A through to W for eg, it could be a major problem for dogs X to Z and if your dog falls into the latter category you're not going to see an improvement :)
Personally I prefer to stick to foods whether dry complete, moist complete, home prepared or raw (or mixture of any/all!) when the diets themselves have *minimal ingredients* - it's so much easier to identify an allergen etc if there are only a few things "in the mix" rather than an ingredient intense diet where any one or many of the parts making up the complete are possible candidates and less easy to remove.
Prescription diets available only through vets are expensive and generally carry a long list to make up the "food friendly" recipe - where some are better than others is that often the most likely ingredients to cause adverse reaction are hydrolised therefore the dog's digestive system fails to recognise something which would otherwise cause a flare up.
Were this my dog I'd change to a different diet entirely with *novel ingredients* (to this specific dog!) and stick with it religiously for several weeks - on the proviso the dog's condition/comfort did not deteriorate.
The fact that your dogs eat a fish based diet and you add further to the fish content by the use of salmon oil
could suggest that a change away from fish would be your best initial option :)
It's very much trial and error to find the best food for each dog - one of yours may well be better left on the existing food whereas the other changed completely away from it!
best wishes, Teri