If your dogs are allergic to corn, try to find a food that is specific for
food allergies. Natural Balance makes food specific allergy foods with
very few ingredients but they are not cheap.
Once you find a good food for allergies, ask the dog food company for coupons.
(some of them will give $ off coupons which helps a little.)
Some stores and dog food companies also have a frequent buyer plan,
when you buy up to 10 bags you get one free.
Also the feed/pet stores sometimes will run specials too.