Hi Jack,
What you are describing sound like run of the mill age/noise related hearing loss. You lose the high frequencies which makes picking noises out hard.
Sometimes it's as simple as wax blocking your ears and easily fixed, but sometimes it is a hearing aid (and hearing protection) that's needed.
If you have a smart phone and some headphones a quick and easy way is to search the App/Play store for "hearing test app"
This is not calibrated but does give a reasonable guide to hearing loss. Not so much how much (depends on your headphones) but rather where you may have (high) frequency loss.
Here is what normally happens to all of us with time: