BREA, Calif.—A rash of robbery-shootings at four Southland 7-Eleven stores left at least two people dead July 11, with police saying some of the crimes appear to be related. The shootings occurred on 7-Eleven’s Free Slurpee Day, with Monday marking the company’s 95th birthday. Brea police said they responded at 4:17 a.m. to a 7-Eleven…