I would say yes to the vet first.. However I wouldn't say hogwash to other things quite so fast. I see you are in the UK but here there is a website that tests food. its called dogfoodadvisor.. It gives unbiased reviews on the food and keeps track of recalls.
You may be surprised at the foods that don't rate as high as you would think. Some excellent foods were sold out to big companies and the quality went way down.