At least half a dozen stocks that Ted Weschler and Todd Combs probably picked for Berkshire Hathaway Inc.'s portfolio are poised to end the year lower than where they started. They include energy companies that have slumped with oil prices; automaker General Motors Co., which has struggled with recalls; and Chicago Bridge & Iron Co., an engineering and construction firm that's down more than 50 percent since Dec. 31. "It appears, on first glance, that Todd and Ted have underperformed the S&P 500 this year," said David Kass, a professor at the University of Maryland's Robert H. Smith School of Business who has studied Berkshire's portfolio.