Sorry to say that I had not noticed this in my wife after her WLS. The only thing that I could suggest is that since he is so short out is that he is not eating the things that might have given his breath the aroma that you are so accustomed to.
OMG.. YES!!! The nurse, that instructs the class prior to my husbands surgery, gave all of the pre-op patients breath mints, as part of their package. The good part, it will get better about 2 1/2 weeks after surgr. it got way better.