Apple's stock dropped 5% on Thursday, its worst day since April, following FTC scrutiny of Apple News and reports about delays with Siri (Jennifer Elias/CNBC)

Jennifer Elias / CNBC: Apple's stock dropped 5% on Thursday, its worst day since April, following FTC scrutiny of Apple News and reports about delays with Siri   —  Apple just wrapped up its worst day on the stock market since April after reports surfaced about delays with Siri and as the company's news app faced regulatory scrutiny.