Pup not eating his food regularly

He’s 8 months old now and not exactly eating his food like he used to. Sometimes it’s 1 meal a day, sometimes he’ll eat breakfast hours late, and supper late if at all, and here lately he won’t touch it if there’s not something like cheese or a shot of stock added in and even then it’s 50/50. Been feeding him purina pro plan puppy at the recommendation of his vet and he has done well on it. We have switched flavors and it hasn’t helped more than a day or two. Vet says he’s a healthy weight and he’s doing good medically, just being a stubborn hound. Have any of y’all encountered this? Did changing food brands help?

We tried Hill’s Science puppy a couple of months ago but it made him sick so that brand is out for him