In the last trading session, U.S. stocks suffered its worst daily drop since late August on the back of the latest barrage of downbeat economic reports pointing to deeper domestic troubles. Among the top ETFs, investors saw SPY lose 1.7%, DIA shed 1.8%, and QQQ move 1.7% lower on the day.Two more specialized ETFs are worth noting as both saw trading volume that was far outside of normal. In fact, both these funds experienced volume levels that were more than double their average for the most recent trading session. This could make these ETFs the ones to watch out for in the days ahead to see if this trend of extra-interest continues.JKG: Volume 4.10 Times AverageThis mid-cap ETF was in the spotlight as more than 28,000 shares moved hands compared with an average 7,000 shares a day. We also saw some price movement as JKG lost 1.4% in the last session.The big move was largely the result of investors’ flight to both growth and stability. This could have a big impact on mid-cap stocks like what we find in this ETF portfolio. JKG has shed 0.2% over the past month and has a Zacks ETF Rank #3 (Hold) with a Medium risk outlook.FDN: Volume 3.06 Times AverageThis Internet ETF was under the microscope as nearly 1.2 million shares moved hands. This compares with an average trading volume of roughly 405,000 shares and came as FDN lost 1.8% in the trading session.The movement can largely be blamed on the stock market sell-off that badly hit the high growth and high beta Internet sector. FDN has declined 5.5% in a month’s time and has a Zacks ETF Rank #2 (Buy) with a High risk outlook.Want key ETF info delivered straight to your inbox?Zacks’ free Fund Newsletter will brief you on top news and analysis, as well as top-performing ETFs, each week. Get it free >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report SPDR Dow Jones Industrial Average ETF (DIA): ETF Research Reports iShares Morningstar Mid-Cap ETF (JKG): ETF Research Reports First Trust Dow Jones Internet Index Fund (FDN): ETF Research Reports Invesco QQQ (QQQ): ETF Research Reports SPDR S&P 500 ETF (SPY): ETF Research Reports To read this article on Zacks.com click here.