I don't know the particular reason crypto currencies are losing their values. It could be as a result of different factors. I feel investors pulling out might also be among the reasons.
This is due to the activities of investors or those that hold these assets selling off these assets. Also the price of Bitcoin is a major player in the price movements of the other coins - once bitcoin price falls, the other coins are likely to fall too.
Well, this present dip actually started on the month of December last year and then there was a high inflation in almost all countries and probably to celebrate the festive season, many had to withdraw their investments to purchase items they need for the celebration or even go into an offline business then. That's my thought as to what caused the present market dip.
This is a common trend at the first quarter of every year with cryptocurrency. There will be less the man for all the cryptocurrency at the first three months of the year as majority of the people spend much of their money during the festive season.