When dealing with allergies, regardless if they're food or environmentally related, it is essential to provide routine grooming as well (which you may already do). I noticed that you have Golden Retrievers, which have a lot of grooming demands. It is absolutely vital that they get shampooed with an appropriate product to routinely cleanse the skin, get their ears cleaned regularly with an appropriate product, & get their ears, paws, skin, & bottoms trimmed routinely. Everything goes hand-in-hand like a delicate circle. If one area is lacking, then it will effect everything else within the circle.
For example, allergies can lead to yeasty ear infections. If the ears are not routinely kept cleaned & the inner ear hair is not kept trimmed, it will effect the impact of the nutritional regimen. The same applies to their skin, paws, etc.
Please refer to this article, which provides a detailed explanation of the specific grooming needs of many dogs: