Rotating refrigerated dog food?

My dog hasn’t been very excited about dry food, so we switched him to FreshPet from Costco. He loved it at first, but now he’s losing interest. Do dogs get bored with their food?

Costco only seems to carry one FreshPet recipe, otherwise I’d try rotating in the same brand. Would rotating between FreshPet and something like Farmer’s Dog likely upset his stomach?

My main issue is that I have a second dog and if the pickier one doesn’t eat quickly, the other will scarf down his brother’s meals…so I’d like for them to eat there food right when I put it down.