NEW YORK (AP) — Stocks closed lower on Wall Street, breaking a nine-day winning streak. Crude prices fell to a four-year low Monday after the OPEC+ group of oil-producing nations said it plans to increase output. The S&P 500 slid 0.6%. The Dow Jones Industrial Average fell 0.2%. Drops in Big Tech stocks like Apple helped pull the Nasdaq composite down 0.7%. Berkshire Hathaway slumped after legendary investor Warren Buffett announced over the weekend that he would step down as CEO by the end of the year after six decades at the helm. U.S. crude fell 2% to about $57...