Following can be the reason for a major drop off.
1)Facebook is banning all ads promoting cryptocurrencies — including bitcoin and all ICO's.
2)Though a number of factors are involved here that jeopardise the money of Bitcoin holders, the worst thing about these investments is zero depositor's insurance to cover up the loss. This is the reason that investment tycoon Warren Buffet calls it a mere bubble and according to James Dimon, CEO of JP Morgan Chase, "It's little more than a "fraud". Looming Security.
3)There is also a speculation that hackers who hacked 534million $ NEM cryptocurrency are trying to sell it off .
What do you guys think will Bitcoin be back to 20000$ value or will it go down further.