Let's check out the Yahoo Finance charts of the day. Apple (AAPL): Shares are up in early trade, around 2.1%. Billionaire investor Warren Buffett tells CNBC that he added 75 million shares of the tech giants stock to his portfolio. Twitter (TWTR): Shares down here, around 2.0%. The social networking service urged its users to change their passwords after a glitch in its internal computer caused some passwords to be readable. Nike (NKE): Shares up, around 0.52%. Last month Nike's toxic workplace culture was revealed and Wall Street Journal reports that CEO Mark Parker apologized to his employees at an all-staff meeting this week. For more on today's big stock movers check out the Final Round, live at 3:55 p.m. ET, right here on Yahoo Finance.