Dogs, like us, have very personal likes and dislikes. Some are picky eaters, some not so much. The trick is finding good things that they will actually eat. You may have to try a different brand. Change his food over gradually so that it doesn't upset his tummy. Treats - well he'll either like them or not. There's not much you can do to make him eat them if he doesn't like them.
Boo can be very suspicious of new foods. He'll study on it long and hard before he'll even attempt a tiny taste. The look on his face you just know he's thinking I've offered him something poisonous.
Having the other two gobble down treats and food usually helps him to come around to trying it.
Yogi has never met a food he wouldn't eat. He'll gobble anything it right down
and then decide if he liked it or not. After eating it the funniest look will come on his face, "Oh Momma! What was that? It was icky!" But the little doofus will gobble down another bite if offered.
Keep trying, you'll eventually find a treat he likes.
