forcing responsive video sizing

Hello poeple, I use rockstar [great theme] in several websites. Some off them I display some video's, however it seems the theme forces responsive video sizing. These are not my words but from the developer from a youtube plugin which I asked for help first because I thought it was the plugin who was causing the problem. The problem is that I cannot resize the video's who are on display This is one of the websites: link this another link2 Hope that you have a suggestion how to change this? Wkr Jack Holland