Without any clear communication, CoinMarketCap has excluded Korean markets. The reason for that is that prices have been about 30% pricier over there and thus giving wrong valuations on their site.
As the prices & graphs tanked, a large number of people were not aware of what is going on and dumped large amount of coins in panic trying to "cut loses", being under the false impression that their coins are crashing.
You'll most probably find your favorite coins being discounted today :)