I bottled my first batch of cider in mid-August. It improved greatly with about a month in the bottle, but by the end of 6 weeks had started to taste off. I used the re-sealable ale bottles with the plastic stoppers that clamp shut to bottles it and kept it in my basement while it aged so it was not exposed to excessive heat. I added campden tablets at the beginning of fermentation but otherwise I had no added chemicals to the apple juice and yeast+yeast nutrient combination.
Is it possible that it kept fermenting or rotted in the bottle? Should I have added something to stop it from doing that?
I'm hoping to bottle the next batch in a week or so and I would like to age this one a bit more.