United States Natural Gas Fund ( UNG) -1.4% Natural gas prices are tumbling for a third day, leading UNG to carve out yet another all-time low. GAZ is taking a hit as well. However, the premium-laden ETN's losses come as it is in the process of testing previous 2012 highs. GAZ's premium has grown to a staggering size, at over 100%. Buyer beware. All prices as of 2:11 PM EST Written by Don Dion in Williamstown, Mass.