Broadway continued to sled down the slopes of January doldrums last week, as sales at most productions declined and two shows ended their runs.Each of those shuttering productions, “Follies” ($878,880) and “The Mountaintop” ($693,128), took advantage of the week’s lowered sales bar to claim a spot in the top 10. In a rare turn, “Mountaintop” became one of two plays on the tuner-dominated chart, alongside “War Horse” ($960,191). Thanks in part to last-minute sales in advance of the Jan. 22 closing, “Mountaintop,” toplined by Samuel L. Jackson and Angela Bassett, posted the biggest increase of the frame, not counting the spike at “War Horse” as it returned to a full week of eight perfs following a five-show sesh the previous week. Also in the top 10, the recently opened “Porgy and Bess” ($878,884) continued to log encouraging sales, with the revival upticking even in the midst of the winter slowdown. Meanwhile, although “How to Succeed in Business Without Really Trying” ($1,319,824) didn’t close last week, the frame was the last for star Darren Criss, who pulled in weekly sales of more than $1.3 million three frames in a row. That kind of proven box office looks poised to put the “Glee” star on the wishlist of many producers as the thesp heads back to work on the Fox skein. Nick Jonas kicks off his stint in the show Tuesday. Almost every individual production on the boards logged a decline last week, with a notable drop at “Sister Act” ($462,966) standing out among a slew of dips at shows including “Mary Poppins” ($621,391) and “Memphis” ($520,530). “Sister Act” was also the only show on the boards this week to see attendance fall below 50%. Broadway cume fell around $1.6 million to $19.3 million for 28 shows on the boards, with overall attendance coming in at 78%. The week’s tally is well ahead of the same frame’s receipts in 2011, but last year’s $12.3 million was for only 19 shows.