Six residents were injured, including two critically, in a five-alarm blaze Thursday morning at a boarding house in Atlantic City that spread to two neighboring buildings, officials said. Two of the residents of the Hotel Cassino were flown to Crozer-Chester Medical Center for treatment, city officials said. Four firefighters were treated for injuries, Atlantic City Professional Firefighters NJ FMBA Local 8 said. “All will be OK,” the union said. ”Three were released the same day and one was admitted for observation.” The fire broke out shortly before 8 a.m. on South Georgia Avenue. Firefighte…