There's a crackdown in China and South Korea which is causing the downward volume. Some coins are junk coins and will go down in volume once the excitement about the ICO is over.
quite the opposite
the "Crackdown" in china actually cause a huge increase in volume because prices fell and that means a lot of action in the market from traders selling, shorting, buying the dips,.... and that happened for every single coin that dropped in price, their volume went up.