@TeamYouTube are you tracking an issue where YouTube videos won’t load or are extremely delayed on iOS/Apple devices when connected over WiFi? Problem is both app and web browser/embeds. iOS/tvOS/MacOS is current version as is the app.
Thanks for letting us know. We haven't seen any issues which are specific to iOS. However, read through this guide to help troubleshoot streaming issues on devices: https://goo.gl/brNJNh