ive got a '93 Fortess one 4 stringer and have only had it a few months but when live i notice a dead spot on the 7th fret on the G string! it plays but lacks any resonance to it and as a result is very much quieter than any other fretted notes on other strings or indeed anywhere else on teh fret board. Any ideas how i can remedy this?? i have a low action and use flatwound strings