A nonprofit gym for seniors and people with chronic health problems may close in March, though the manager hopes businesses will help the fitness center relocate by renovating a warehouse across the street. Active Life Fitness Center has been unable to pay rent at its 1820 N.W. Mulholland Drive facility for several months. Property owner Lew Marks said he is negotiating with another potential tenant. If he reaches an agreement, Active Life Fitness will have to move. Marks said he supports the fitness center’s mission and has offered free space across the street in a warehouse he owns. Active Life …