the nut is the piece of plastic at the top of the neck above the first fret, the things you adjust at the bridge are bridge saddles. it sounds to me just like its a dodgy string, i cant see why just the e string would be distorting and not the rest, have you tried a different e?? as far as i know, all basses should have no problems no matter how heavy or light the strings are, providing they are set up well