The S&P 500 was down 0.6% to 1,976.88.
The Dow Jones Industrial Average was down 0.6% to 16,549.57.
The Nasdaq was down 0.6% to 4,799.44.
The yield on a 10-year Treasury bond was down 0.1% to 2.18%.
The price of gold was down 9.1% to $1,133.
Irvine-based Masimo Corp. was down 2.6% to $40.44 and a $2.1 billion market cap. The device maker had by midday traded shares at a rate above its 90-day average.
OC-based chains that jumped Friday on an analyst upgrade gave back some of their profits in midday trading.
Irvine-based Habit Restaurants Inc. was down 4% to $24.93 and a $644 million market cap.
Costa Mesa-based El Pollo Loco Holdings Inc. was down 3% to $13.27 and a $519 million market cap.