11 month old stopped enjoying his kibble

First of all I know I need to discuss this with the vet and I will to make sure there are no underlying issues like allergies or gum/teeth problems.

My baby has been eating the same food (Purina Pro Plan 30/20 puppy, chicken and rice flavor) since he started solid foods with his breeder. I’ve joked that there was nothing that would stop him from eating.

Recently had to take a month of antibiotics for a lingering cough. While he was taking the medicine he would get peanut butter with the pills hidden inside on top of his food. Now that he’s done with his medicine, he is no longer getting peanut butter and has therefore lost interest in his food.

I’ve tried giving him his food in different ways (via snuffle mat, puzzle feeder, frozen Toppl). I thought maybe the food had gone bad and got a different bag. I thought maybe he was developing a chicken allergy so I started integrating salmon kibble into his bowl instead.

The only thing that can get this dog to eat is when there is a topper on his food. His breeder recommended giving him a probiotic to help regulate his gut after all that medication so I had been using the Fortiflora liver flavored packets on top of one of his meals. When that topper is on, he scarfs his food down just like he used to.

Does anyone have any experience with teenage Basshole picky eaters? Until he is regularly eating his kibble again I’ve cut out all treats and he never gets tabl scraps.

Is the solution to just stick with the plain kibble and withstand his hunger strike? Again, I will be discussing this with his vet but any pet owner advice would also be appreciated!