By Gerry Shih SAN FRANCISCO (Reuters) – Twitter Inc reported lackluster user and usage growth for the second consecutive quarter on Tuesday, deepening investor concerns about its struggle to gain a mass following. Twitters stock fell more than 10 percent after hours to $38.05, below its post-initial public offering low of $38.80 on November 25. Perhaps most worrying, the San Francisco-based company said its 255 million monthly users, on average, appeared to check the service less frequently than a year ago. The results revealed slowing momentum at a company that exuberant investors just six months ago had argued could one day match Facebook Incs scale.