EQ accepted practice?

OK, am I permitted to go back to my final mixed down wave and apply a bit EQ at the high end just to take a bit of the bite out of the upper registers?

why I ask is - I mastered down a song using Yamaha Final Master - now the final mix sounded good - after the master it still sounds good, I let the bottom end breathe and adjusted all of the settings until it sounded good, but no matter what - my high end on the guitars seem a bit to high - they still sound good, but it can be better...so..

could I apply a bit of eq before mastering the song - or should I do the right way and go back to the original track recording and stick and eq there and make adjustments to my sound for future recordings?

reason is I have a cd's worth of tunes that no doubt will show the same issue when mastering, can I get by with 'cheating' this time or should I apply EQ to each of the multitrack projects?

thanks for any input.

definitely fix it in the mix. if you are sure "that sound" is coming from the guitars only then i would go back and roll it off in the mix rather than later. as a rule i drop quite a bit of high-end on distortion guitars since the warmth and tone typically doesn't go beyond about 10k (a number grabbed out of my head so don't quote me on it) or so, particularly in a full mix where you want the vocals to be heard and nice sounding cymbals.

in short you may dull the whole song instead of just the guitars.