I think there are many reasons for the decline in the price of Ethereum.
1. There are too many ICO frauds, causing investors to abandon the purchase of ETH for investment.
2. The fraudster sold a large amount of ETH in exchange for fiat money, resulting in a panic selling.
Their are other factors such as the manipulation of whales and other that help to dump Eth price. Ethereum will correct its price but it will take a long amount of time , hopefully when it bitcoins correct its price , Ethereum will correct its price too.