this is because bitcoin is a bubble and now it is starting to pop resulting for the value to drop drasticallly without any further notice. i believe that it can still continue to go down and this problem is something that we should worry about. in my case im now starting to convert my coins into our local curreny which is ( php ) because im affraid that this event can last longer and ill be ended up loosing instead of earning a profit with my invested bitcoin. though im still hodling my altcoins because i feel confident about the state of altcoins even if they are falling sometimes just like bitcoin but they usually recover on a specific date.