Broadway box office had an unmistakable case of the early-fall doldrums last week, with tallies at most individual shows dropping and the overall total falling well behind the cume logged over the same week in 2011.Year-to-year dip was attributable in part to Broadway Week, the annual fortnight of 2-for-1 ticket offers that helps keep attendance high during the historically slow weeks of early September. Whereas this year Broadway Week ended Sept. 16, last year during this frame the offer was still in effect. Last week’s overall Broadway total added up to $17.1 million for 22 shows on the boards, vs. $18.5 million for the same number of titles during the same frame in 2011. Last week’s attendance of 183,074 pales in comparison to the 207,000 posted last year at this time. (Compared to the prior sesh, last week’s cume was down some $330,000.) Among the handful of shows to report week-to-week bumps in sales last week, one of them, “Porgy and Bess” (up almost $100,000 to $891,566) can trace its growth to last-minute biz ahead of the show’s Sept. 23 closing. Paul Rudd and Michael Shannon starrer “Grace” ($465,332 for its first full week of previews) also pulled in far more than it had the previous sesh, when it had played only three previews. The new play by Craig Wright has so far proven relatively healthy at the box office, given its early-fall start date and its unfamiliar title. In the Top 10, “The Book of Mormon” ($1,626,122) continued its reign on top, again besting “The Lion King” ($1,555,752) and “Wicked” ($1,495,735). “Evita” ($1,045,494) slid by a hefty 11%, but still stuck it out in the millionaires’ club. Among the hardest hit last week were “Peter and the Starcatcher,” knocked down 21% to $294,536, and “Bring It On,” sliding 16% to $371,851. Producers of these two newer shows were likely expecting grim sales in September, but both teams must surely be waiting anxiously to see how much B.O. will pick up when Broadway activity gains momentum later in the fall.