PHILADELPHIA The Fox News skybox here turns into a hive of activity as the networks star anchors analyze the Democratic National Convention for millions of viewers. When the cameras blink off, however, the banter has been replaced by something rarely heard in the television news business: silence. Megyn Kelly and her co-hosts, including Bret Baier and Brit Hume, have not been speaking during commercial breaks, according to two people with direct knowledge of the anchors interactions, who described the on-set atmosphere at Fox News as icy.