How long should I wait before changing his food?

Me

I posted a couple weeks ago about how my dog had some diarrhea and an upset stomach and how we did a bland diet. He’s currently eating the wholehearted puppy food but I was told by someone that taste of the wild would be better for him and his stomach. I was also told that it has a better variety with the food flavors (my dog gets tired of having the same thing after awhile). He currently needs more food now and I was wondering if I should wait another couple months before switching to that or go ahead and do it now.