Drip, drip, drip. Janet Reno’s plumbers are back on the job, mounting yet another investigation of leaks to reporters. It’s a subject that seems to have a particular fascination for her, though such probes rarely yield anything conclusive. The impetus this time is a Feb. 27 Wall Street Journal item saying Department of Justice prosecutors had recommended indicting former Republican National Committee chairman Haley Barbour in connection with his solicitation of funds from an overseas businessman. The spate of probes to track down loose lips in the halls of Justice -— including one to find the source of a Washington Post story from last year about intelligence findings on the Chinese plan to influence the 1996 elections -— “have changed the whole atmosphere around here,” says a senior Justice official. Clearly they have left the department’s Office of Professional Responsibility with a near impossible task on its hands: everybody resents these leak investigations, and nobody wants to talk.