A weak update on China sank the stock.While the broad stock market was soaring on interest rate cuts today, Skechers (SKX -9.62%), the casual footwear specialist, was moving in the opposite direction, tumbling after it told investors that China sales were weaker than expected at an industry conference.As a result, the stock finished down 9.6% on the news. China struggles continueSkechers is far from the only U.S. consumer-discretionary company that's struggling in China as Nike, Apple, and Starbucks have al ...