证券板块集体走低，长城证券跌超5%

Group 1 - The securities sector experienced a collective decline on September 18, with several companies reporting significant drops in their stock prices [1] - Changcheng Securities fell over 5%, while Shouchuang Securities and Guosheng Jinkong both dropped over 4% [1] - Other companies such as Guohai Securities and Xinda Securities also saw declines in their stock prices [1]