The Bloomberg China IPO Index dropped 10 percent from its high on May 27 through Wednesday, while all 10 of this month’s worst-performing companies in the benchmark Shanghai Composite Index are IPOs from the class of 2015. Jiangsu Broadcasting Cable Information Network Corp., which peaked at 197 times earnings after 23 straight days of post-IPO gains, has since lost 39 percent. The turnaround is a sign that China’s equity rally has gone too far, too fast as investors lose confidence in some of the market’s best performers, according to BNP Paribas (China) Ltd.