The sell-off resets expectations and brings the multiple down -- but buying now could be a mistake.Shares of Lululemon Athletica (LULU -18.59%) plunged after the company's quarterly update late last week. The sharp drop in the athleisure apparel company's stock worsens what has already been a rough year for the stock. Shares fell hard following the release of second-quarter results and a guidance cut tied to tariff costs and softer U.S. demand.The drawdown looks more like a sharp reset than a broken busines ...