Lumentum, a supplier of high-tech components that Apple uses in its iPhones for facial recognition, lowered its outlook on Monday for production volume of iPhones. The memo was apparently enough to panic Wall Street investors who have been nervous about the prospects for the company’s latest iPhone models going into the holiday season. The news, coupled with a disappointing earnings report from Amazon, set off a retreat from the tech sector. By day’s end, the Dow had plummeted over 600 points.