Yes.
Bitcoin sound money and these drops overnight are very normal happenings in the market. And whenever it drops a lot, you'd see the domino fall because the altcoins market are also following. So the reason for this is simple, Bitcoin is highly volatile and that's why it moves a lot from time to time but sometimes, it doesn't move at all for a couple of days. But when it does, expect that it's only two of it, either up or down.