i think some whales are afraid too lose the chance to have money. that's why they pull it out when the price of bitcoin reach the high bracket price . when they pulling their money out of their wallet bitcoin price is affected because whales are commonly seen at the market and the market has a lot of part in terms of bitcoin price.
I think its not a whales its just a normal down fall of bitcoin and base in my research today about the news in bitcoin i think there's no reason behind it.
Mostly the news today are price drop of ETH and they are talking about ethereum will be fall at $13 usd again..
As i can seen almost all altcoin are affected from the price fall of bitcoin..