BTC/USD fell sharply over the weekend:
It can be a volatile beast, thinly traded. Relevant catalysts seem to be absent.
Perhaps the folks reading about the "halvening" are taking it the wrong way? Its not the price that's the halvening is all about but the supply (the imminent supply shock, once it's taken place only 900 new Bitcoin will be entering circulation each day, from 1,800 in place the past four years).