It's gross! Janitors hit Equinox gym sex BY BARBARA ROSS and BILL HUTCHINSON DAILY NEWS STAFF WRITERS Several disgusted janitors are dishing dirt on the Equinox fitness center chain, claiming in a lawsuit filed yesterday that the upscale gyms are used as sleazy gay sex clubs. The six janitors charge in the Manhattan Supreme Court suit that they are fed up with cleaning up after male gym members engage in "explicit sexual activity." The janitors cited five Manhattan clubs, including the chain's flagship gym in the Time Warner Center at Columbus Circle, as places where "lewd behavior" is rampant in...