Hi H, l am a vintage MN freak too!
l have a 50ml glass bottle of the vintage EDT with the black plastic "shoulders", is this the one you mean, or are your bottles completely plastic? l got mine from ebay last year, & although the top notes may have turned slightly, it still smells as deep, dark & delicious as l remember it, not in any way watery or alcoholic. lt does sound as if you may have been unlucky enough to get two dud bottles; l wonder if the bottle has something to do with it; does plastic preserve scent less well than glass??