This coincides with the sudden drop in Google searches for bitcoin and others, also I've noticed the number of users online on poloniex has dropped significantly. This seasonal pattern was first observed with bitcoin, check this out: https://medium.com/@octskyward/bitcoin-s-seasonal-affective-...

Also, other negative news: 1. Alphabay, the largest darknet market went offline, not sure if that is significant. 2. Bitnumb, largest(?) crypto exchange in South Korea got hacked, also not sure how much impact this had, but usually an exchange hack has a short term effect on prices and there has been a lot of recent activity in SK.

Other reason may be that boom and bust cycles are a natural occurrence of crypto markets. They were getting white-hot for the last few months and finally need some time to cool. So move along, nothing to see.. The cycle continues. The next boom might be bigger than anything we've seen before :-)