The second week of CBS’ Under The Dome (2.8/8) saw a few cracks in the new drama’s strong ratings shell. Following its big debut last week, the Amblin TV/DreamWorks TV-produced show was down 15% on Monday — not altogether unrespectable retention levels for the series based on Stephen King’s 2009 novel. Under The Dome was easily the top-rated show of the night and by far the most watched with 11.52 million viewers. Otherwise, CBS was all repeats Monday. Like on most almost-holiday summer nights, usage was down 5% among adults 18-49 and dipped 4% from last week. CBS was tops for the night in adults 18-49 and in viewers with 7.08 million.