Pueblo walked off the job Sunday morning after a temporary contract extension ended with no agreement. Employees at the Safeway distribution center in Denver also joined the strike. Understaffed stores, changes to health benefits and low wage increases are top issues for the union, as has been the case since the first contracts began expiring in January. The union also accuses managers from Albertsons-owned Safeway and its rivals at Kroger-owned King Soopers of unfairly teaming up to negotiate. That’s threatening to take benefits away from its Safeway members, said Kim Cordova, president of United Food and Commercial Workers International Union...