Shares of dietary supplement retailers tumbled in heavy trading volume on Tuesday, spurring a surge in options hedging activity for those stocks even though fears they would be mentioned in a U.S. Department of Justice lawsuit did not materialize. GNC Holdings’ shares tumbled as much as 27.1 percent to hit their lowest in four years, but closed 6.4 percent lower at $29.07. The DOJ called a press conference at noon Eastern (1500 GMT) about criminal and civil actions aimed at stemming the sale of unproven nutritional supplements.