LONDON, March 31 : Tether has let go two senior precious metals traders it hired from HSBC only three months ago, a source with direct knowledge of the matter told Reuters on Tuesday. El Salvador-headquartered Tether cut the roles as spot gold prices headed for their steepest monthly drop since the 2008 financial crisis, pressured by fading expectations of rate cuts and rising energy costs amid the war in Iran. Tether held about 130 metric tons of physical gold backing its products as of end-