After that, you are using av Player /JWPlayer for videos and it's not mobile ready
It render videos with fixed 510px width so videos won't scale.
2 options:
1. Find a version of that module that is mobile ready supporting fluid videos
2. Assign responsiveness to div.jwplayer and div.avPlayerContainer
There is a parameter in Responsivizer named 'Responsive elements selectors', if you add:

div.jwplayer, div.avPlayerContainer

that should do the trick.