When shares of Chipotle Mexican Grill Inc. peaked on Aug. 5, 2015, four top executives held stock appreciation rights worth $225 million. For now, they're worthless. A plunge of more than 60 percent since then has erased paper gains of $37.5 million for Chief Executive Officer Steve Ells, $34.8 million for Chief Financial Officer Jack Hartung and $10.7 million for Chief Marketing Officer Mark Crumpacker.