The illness that sickened Hillary Clinton with pneumonia and caused her to have to be escorted away from September 11 ceremonies in New York on Sunday also struck down several members of her campaign team at Clinton headquarters in Brooklyn, PEOPLE has learned. "Everyone's been sick," a campaign source tells PEOPLE. At the end of August, two weeks before Clinton was diagnosed with pneumonia, a debilitating bug was making the rounds among staff at her headquarters and campaign aides who travel with Clinton, a source tells PEOPLE. At least half a dozen senior staff were felled, including campaign manager Robby...