Downturn?

It's a combination of factors.

1) Crypto Scams. Someone buys a coin that is essentially an elaborate scam, gets ripped off and tells someone. That news spreads. Then another victim and another victim and that puts a bad taste in one too many mouths.
2) Media hype and media scares.
3) Exchanges that are making money off investors by slowing down transfers, adding fees and pretty much screwing around for the highest possible payout. This can also be holding funds, placing extreme holds on deposits so that the depositor misses out on a price value etc. Other times it's the trading price of a coin 5-10X the actual legitimate price on other exchanges also blocking out deposits of that particular coin to keep others from benefiting off of this "in house" price manipulation.
4) Massive sell offs back to fiat
5) Too many coins coming out at the same time meaning the funds between coins are being spread too thin. Too many people have diversified their coin collections into the hundreds of coins which has caused some noticeable drops on the main coin's value. The reason that's also happening is that coins that typically are traded against LTC and maybe Doge markets are now being placed in the BTC markets. So people are trading more BTC or ETH for these alt coins yet are essentially cause the value of both BTC/ETH and the alt coin to fall. it's a vicious cycle. Example: Ethereum based coins. You'll notice strong sways in pricing over the last month as more and more eth based coins hit the market. People sell their ETH to get a particular coin ultimately dropping the price of ETH, panic and sell back at a loss on both ends.
6) ICO fraud and scams being exposed.
7) Airdrop scams