So when I play a youtube video the Now Playing widget changes to playing that, this is only happened from the recent update. I was wondering if there was a way to get it back to where it only controlled music players whilst keeping the artwork, artist etc layout of the Now Playing Widget?
This has always been like this. It works the same as the "now playing widget" in the system notification center and displays all apps that support the "now playing API". If you want only spotify you'd need to create a apple script based widget, you will find some of these in the presets section, however they consume more energy.