Facebook Inc. (Nasdaq: FB US) fell as much as 4.3% to the lowest point since July after warning Apple Inc.’s new data collection restrictions will hurt its third-quarter results. The stock’s tumble reflects investors’ concern that Facebook is already seeing declines in its digital advertising business after Apple implemented a software update to limit targeted advertising on iPhones. Facebook Chief Financial Officer Dave Wehner previously warned that Apple’s changes would have a greater impact in the third quarter. Facebook shares are 25% higher this year.