Eddie, I just tried to duplicate your problem and I exported all tracks in one instance, then separate tracks in the next instance. No noticeable change in volume.

I would re-check your settings in BIAB and/or try Return to Default Settings (sic) and test anew. Stating the obvious...something is amiss in your rendering to .wav settings. What happens when you try rendering to .mp3 or .wma? Same problems?