My puppy was 45days old. And it was given rabbies vaccine instead of 9-in1 vaccine what to do now

I own a Rottweiler who is 3 Months old. It is growing very good and active when I am feeding Royal Canin Junior-Rottweiler. I have recently heard that Drools focus is also making its mark in Large/Giant breed dogs. But When I feed him Drools focus(Same amount of Royal Canin), he lost weight and became Inactive. He is eating it with same interest as he used to. I checked the manufacturing date and it was manufactured on 5th may 2015. Suggest me some tips for making my rottweiler gain weight. Any tips/food brands/feeding Food quantity tips or anything is appreciated. TIA