Brewed my first beer, IPA (all grain) which tasted great when carbonation was complete. Was fine for 3/4 days, nice and hoppy, smooth but as the days pass I am noticing a slightly bitter taste develop. It's the aftertaste which isn't quite right. I guess it is kind of metallic/earthy but slightly strange that it wasn't there from the outset? - Again, if it were green, it would have been there from the beginning?