Don't get lost in a world of options. Remeber what's at heart at the recording... The Performer. It may sound good to you, from within your own body, but If there's nothing obviously wrong in the recording chain, get used to the fact you just have a muddy sound. Try recording as pure as you can. I.e. no EQ, no hardware effects or compression. Once in the computer, take a short break and come at task with fresh ears.
A typical method for finding out problematic resonances is to use a parametric EQ with gain to full, and scan across the spectrum untill you find this 'muddy' sound at it's worst. Now bring down the gain, and cut away this frequency, only use as much cut as you need, using any more can harm the sound and reduce the Q untill this muddy sound starts making a reappearance. Only deal with one EQ at a time as again, don't get lost in a world of options! In the music tech world there really are a fair few!