If yours are genuine, than it looks like there its very difficult to detect a fake from real ones. The changes could be caused by a change in production process?
Mine are only 3 months old and sound great, very detailed, sometimes bit bright but nothing to worry about.
Fake or not, only the sound quality can determine that.
I checked mine with a magnifying glass and on mine L and R are engraved, just like the Yamaha logo at the back.
I won't worry about the grooves, also have them but I can not see them with the naked eye.