I have two machines running El Capitan with all the latest updates installed, my mini and my MBA. Browsing the same site yesterday on both machines, the Air played the video streams in HTML5 including an option in the player controls to send the video over AirPlay whilst the mini plays as flash. The mini also struggles on YouTube, often giving me error messages about non-compatibility, while the Air just plays HTML5. Clicktoflash is installed on both so I have no idea what's causing the difference. Any thoughts?