By Bret Kenwell Bitcoin, ethereum and other cryptocurrencies are crashing, but they’re also approaching must-hold support. On Sunday night, the futures made it pretty clear that the stock market was not going to have an easy open on Monday morning. However, because cryptocurrencies trade 24 hours a day, seven days a week, we already knew that bitcoin, ethereum and others were enduring a painful start to the week. At one point on Monday, bitcoin was down 15% and ethereum was lower by 18.8%. Both are now down about 12% on the day, as bulls look to stir up some sort of bounce. We talked about bit…