lately i ve been noticing sum string buzz in 6th and 7th string of my s7420...so i raised the action of bottom strings...now its fine.... still getting some buzz wen i play djents though....but the thing tats botherin me is the string height....i measured it and found out tat for lower b at 24th fret its around 5mm...i mean is it normal or am i doin something wrong??? do i need a truss rod adjustment or gettin a lower b of higher gauge will help???
Then it's an action issue. Play around with the action a little until you can get to the lowest action at which the string no longer buzzes. If the string is much higher the rest there may be a fret issue.