Earnings have fallen due to more headwinds with its banking franchise.Shares of Charles Schwab (SCHW 0.34%) fell over 15% this week, according to data from S&P Global Market Intelligence. One of the largest brokerages posted slow growth and poor earnings as the company still deals with low-yielding assets on its balance sheet. As of 1:31 p.m. ET on Friday, July 19, Charles Schwab stock was down 17.5% this week.Here's why.Slow growth and headwinds on the balance sheetThis week, Charles Schwab reported earnin ...