Whose selling!? I would think being the market is always right that many people know something you and I do not know.
Demand destruction, competition, reduced gross margins, inability to mine (strike). Whatever is occurring is real do not assume you have been endowed with the power to have recognized a bottom as something declines. Rather assume you are not the most unluckiest person in the World to short something in a downtrend that then reverses. The latter is a lot more probable.