I brewed an Imperial Stout and was aiming 1.099, but got 1.090 OG (By adding 1 pound of DME) After 13 days, my FG was 1.022 which was exactly my target.
5 months later, I took a reading and got 1.012. I tasted it, it's hard to tell if there's an off flavour. Beer is an intense 10.5% ABV having bourbon and wood in it. It's really good, but I don't know if I'm looking too hard to detect something different, after several sip I got a weird feeling that lasted quite a long time.
Might it be contaminated? Dangerous to drink? How to know?