Ok. So I've had an Epi Les Paul since 2005. It sat neglected in it's case for the last 2 or 3 years. Got it out in October of 2020 and changed the strings. It's been sounding fine the last few months but now it's doing something weird. Clip on tuner says strings are in tune, I've tuned the guitar to itself, still sounds good. But as soon as I do anything on the two low strings around the 2nd and 3rd frets, it sounds out of tune. It's most noticeable on Stairway to Heaven when you pluck a lower string and a higher string at the same time. I'm hoping this is an easy fix as I don't have spare funds right now to have a tech check it out. Anyone have any tips?