I'd try something other than Eukanuba, which has a few potential triggers for tummy problems. You want a protein source that isn't chicken or beef, to start; and nothing like 'poultry meal'.
Most dogs will readily take to another food -- try mixing a fourth of the new into the old and gradually increase til the original is replaced, over a week or two.
Also ignore a dog that refuses food -- there's advice under 'finicky eaters' in the Library section. In almost all cases, refusing to eat isn't an issue of liking or disliking a food, but of holding out to see what else will be on offer or because they quickly realise owners start to give lots of extra attention if they don't eat (eg coming over, fussing, hand-feeding, encouragement etc). They are very smart at figuring out they get rewarded if they *don't* eat with extra attention or new foods!