A number of top stocks from IBD’s 33 sector groups showed weakness amid the market’s sell-off Monday. TAL Education Group (XRS), a provider of after-school tutoring services in China, slipped below a three-weeks-tight buy point after falling 1, or 3%, to 34.59 in mildly above-average volume. The stock ended 3% below the 35.55 secondary entry, which gave existing shareholders a chance to add a small number of shares to their holdings.