Page Speed with Video

I have three websites for my sons business MattFurness.co.uk, SessionDrummer.co.uk and DrumTeacher.co.uk. Today I checked the PageSpeed Insights on the home page of all three (which use the same Rock Star Pro theme) and the last one has considerably superior load times to the other two. I have been through the Additional CSS and checked plugins but nothing seems to improve the first two. All three are very similar in structure so I would not expect large differences. I am now coming to the conclusion that it is the YouTube videos feature which slows them down. Does it really have such an impact? Have I coded something wrong do you think? Many thanks, Chris