Fret buzz on Yamaha TRBX

[Bassique]

I recently changed strings for my Yamaha TRBX505 and since then I've been getting buzz from 5th and 6th fret on the low B string. I tune to drop A and the gauge is .145 and seems that the buzz is coming below my fretting hand which is a bit weird. I've tried adjusting the truss rod and also change action but nothing seems to help. Could it be that its "too" thick string for medium frets so even small resonance hits the frets after the fretting hand? If I tune it to B, it seems to get better.

 

[bobdabilder]

Make sure strings fit the nut properly and set witness points and adequate break angle to the tuner

 

[Bassique]

Thanks, filing the nut actually helped a bit.