one of the things you may want to check into is if the neck is over straight. if you have an over straight neck with no relief and play with a light touch the strings wont necessarily buzz like they would for someone with a normal attack but they'll be slightly muted. i sat for hours and hours and hours adjusting the pickup height thinking "no cant be the action thats messed up..."
though the neck is the main thing that goes out of whack per say... the bridge does after a long period of time need to be adjusted.