The company is reporting slowing growth and guiding for an even larger slowdown this quarter.Shares of The Trade Desk (TTD -1.03%) fell by a sharp 37.1% in August, according to data from S&P Global Market Intelligence. As of this writing on Sept. 3, The Trade Desk is down 55% this year and in the middle of its worst price drawdown ever.Investors are concerned about slowing revenue growth for this advertising innovator, which has previously traded at a premium valuation. Here's why The Trade Desk slipped yet ...