Then I have your answer...it's a 3x leveraged ETF and it's the end of the month. By nature and design, these instruments are designed to deteriorate. Generally they follow 2 front month contracts. What this means is as each day passes, they sell a little of the front month, and by a little of the next month. Aside from when a market if tanking (this one is a bear ETF), the nature of the instrument is to buy high and sell low.....this is why you see a lot of these 3x ETFs do reverse splits (NUGT just announced one). At the end of the month the rebalancing is often magnified.
News 
Market Data 
Discover 
