Maybe one of the reason is crypto currencies were got banned from Google, twitter, facebook and in instagram, these kind of action from the assets of crypto currencies can really affect the market situation. Aside from this their are many panic sellers in the market that oftenly shaken when their is undesirable situation of the crypto currencies.
Although this does seem like a good reason for the prices to fall, I can't help but wonder that the new of the ban has been around for quite some time now so why is it just affecting the prices now? My bet is on a dump and someone should check if Mt Gox is selling again as they still have a very large amount of coins left to sell and there is no doubt that selling those coins will really affect the prices of the coins.