Forgive me if this has been asked before - I did a search, found a couple of close topics, but not exactly what I'm looking for. I have some buzzing that occurs only when I bow fortissimo on the open G and D strings - mostly the G, but a little on the D too. I do not have any buzzing anywhere else on the fingerboard, not even first finger in half position (e.g., the Ab right above the open G) and it's only when I'm really digging in, so it's not that big a deal, but the perfectionist in me is still bugged by it. I don't believe my action is overly low - 6 mm under the G, 9 mm under the E, measured between the string and the bottom of the fingerboard (and Original Flexicores, BTW, if it's relevant). I'm hesitant to raise it much more, given my struggles with tendinitis and CTS. I am concerned that the nut might have been filed a bit too low, but I don't really know what the standard is. I can say that I am able to slip a standard thickness business card under the open E and A strings, but not the open D and G strings, if that's any help (I'm afraid I don't have anything to make more precise measurements). If the nut was cut too low, I assume I just need to make a trip to a local string tech for some work - I'm guessing some sanding the fingerboard a tad right by the nut will be in order. However, if it's a setup issues that I might be able to correct myself, I'm all ears. Thanks much in advance.