Newbie question alert. I have an Epi LP which has a slight fret buzz issue.

On the D string around the 12th and 13th frets, I get some buzz. I don't seem to get it higher or lower than that.

Any suggestions? Should I just raise the bridge a fraction and see if that helps?
That's what I'd recommend doing, it's easily adjustable, and you could always set it back if you're not happy with the higher action.
If its really such a small amount (can it even be heard when plugged in?) and you're happy with the action then you may just want to leave it.

If it's really annoying you or is audible through the amp then you should be able to adjust that individual string height iirc.