SANTA ROSA, Calif. — Nick Gravenites, the blues singer and guitarist for The Electric Flag and songwriter for Janis Joplin, has died, his family announced. He was 85. “I regret to inform all of you that Nick passed away last night,” the Gravenites family wrote in a post to Nick’s Facebook page. “Details to follow as they arrive. The Gravenites family appreciates all of the fans and loved ones who have been there for us during this time.”