From what i've read on different news online about cryptocurrency, price drops due to the increase of supply but decrease on demand. This started when bitcoin and some altcoins increase its price this last december 2017. Investors got hype and started investing more on that particular coins. As result the supply of those cryptocurrencies increase and the rate of demand decrease. That's why the high price of coins could not be sustained, resulting to gradual decrease of prices of cryptocurrencies.