Charles Schwab's Nathan Peterson turns to the S&P 500 (SPX) price action and explains why he's "cautious" as concentrated positioning ramps up in the index. He tells investors to brace for Micron's (MU) earnings as the stock seeks to jump a high bar. Kasey McCurdy offers a closer look into the market dynamics and the "sensitive" environment that he sees accelerating upside and downside moves.