The tech-heavy Nasdaq composite plunged 110 points, or 2.6 percent, to 4,127, its biggest drop in two months. Other major indexes fell, but not nearly as much. The S&P 500 index fell 23 points, or 1.3 percent, to 1,865. The index traded at an all-time high earlier in the day. The Dow Jones industrial average lost 159 points, or 1 percent, to 16,412.