The stock could still be suffering from Morgan Stanley's downgrade to Underweight on Monday. Moreover, Morgan Stanley set the target price of the stock at $33, which was approximately half of the Monday closing price. The downgrade stemmed from concerns over Twitter's ability to compete with Facebook (FB) and Google (GOOG) for advertising money due to its limited advertising avenues.
Twitter's IPO came in Nov. 2013 and peaked at $74.73 on Dec. 26, 2013. Since then, the stock has fluctuated until the drops of the past two days.