My akg headphones which came with my s9, the right hand bud has all of a sudden gone really quiet for some reason.
Any ideas as to why?
Most likely a defect. I don't really use headphones or earphones but that's what I personally assume the problem is. Return them to Samsung and get a replacement if possible. I know such things are annoying but on the bright side, my S9 has a screen problem - burn in from watching too many YouTube on portrait mode. So I had to go to a store as well. Since there aren't any Samsung stores in my country (or at least that 'advanced' ones), I can't really give my phone to Samsung for screen replacement. All they offered me is sending my phone to the USA but that would take months, and I actually need my phone daily, so I refused, as much as I hate that burn in. Another option is sending it to a third-party replacement shop but I don't trust them. They will probably steal all my original hardware and replace it with a knock-off one. So if there is a Samsung store in your country that would replace the earphones, don't miss the chance.