Electric guitar: 5th fret, 2nd and 3rd string "plunks"?

If this is a guitar that has seen a lot of use, you probably have some frequently-played (and consequently, worn) frets that are causing the strings to contact the less-played (and higher) frets. If the guitar is fairly new, it is possible that some of the frets are not fully seated, causing the same problem. Using a straight-edge will identify the offending frets, and the appropriate action (e.g., dressing or re-seating) can be taken by a qualified technician. Not a big deal to fix. Best regards, Dana