A lot of lower-quality foods add a lot of sugars and chemicals to make the food more palatable for dogs, so switching to a new, better, more natural food may be harder because the dog likes the taste and aroma of the not-so-good food. Maybe try getting a couple of cans of Wellness Core and topping a mix of RC and Wellness Core (the kibble) with it, and see if that helps. If so, slowly eliminate the RC, and then slowly eliminate the canned topper (unless you want to keep it – it is even better for dogs anyway).
I often make my Rat Terrier mix a “soup” of canned and kibble, and you can add as little as 1/2 teaspoon (or more, if you want) of canned and mush it up with the kibble and a bit of water until it is flavorful and soupy.
Also, another posted had asked a similar question about picky yorkies, and in the end, if all else fails, you could always just let them eat it when they’re really hungry – just leave it out, and if they haven’t eaten it in 2 full days (or so), then you can add a topper. But dogs usually figure out that if they want to eat, they’ll have to eat what’s available.
