fret buzz when playing octave C's
I have fret buzz when I play octave C's. 8th fret on the E string and 10th fret on the D string. The buzz occurs at the 7th fret on the E string. I was somewhat alarmed to discover this. So I went up and down the whole fingerboard to see if it happened with any other octaves and the answer is no. But I need this fixed because it is in a Bach piece I am working on and it is intolerable.
Obviously this is a neck or fret issue and not a bridge issue. Before touching the truss rod, though, I thought I'd solicit some help here. Any advice from anyone is quite welcome. The bass in question is my MIJ Geddy Lee Fender Jazz. I have DR Fat Beams on it. They are one month old.