I bought a bottle of Bowmore single malt at a duty free shop in Singapore Changi Airport. Opened it during a family gathering. It was lovely and extremely smooth with a slight smoky woody flavour. We finished half of it and I brought the rest home. 2 days later, I had a bit of it on the rocks. It tasted like the worst scotch I had ever tasted. Bitter with a kind of petroleum or chemical aftertaste. How did a good smooth scotch turn into the worst tasting stuff in 48 hours?