The beauty brand is still reeling from a weak earnings report in August. The stock of e.l.f. Beauty (ELF -0.42%) fell 27.2% in September, according to data from S&P Global Market Intelligence. A fast-growing beauty brand taking market share from incumbents, e.l.f. Beauty rose to investor fame after accelerating revenue growth to nearly 100% in recent years. Now, it has revised its guidance downward for the upcoming fiscal year, leading investors to sour on the stock. Here's why shares of e.l.f. Beauty sank ...