Are your dogs having health problems on their current food? If not then there is no need to switch. The less you switch foods the better for the dog.
Guess i should have given more info. My beagle seems to scratch alot. I do find fleas on her, and have used advantage and frontline. I recently switched to K9 advantix, and that seems to have gotten the fleas! but, she is still scratching alot, which makes me think allergies, so i would like to try a new food. Currently, she eats blue adult (from petsmart). i don't have many stores to choose from for food, so nutra, and the others that seem to be popular on this site aren't an option. Thanks!!