Maybe you toggled Play>Level Playback Volume

so... without me doing anything, today the videos play at the normal level again.

that seems legit but literally last week they played at the same volume as all the music :/

Most likely the sound of the video is just lower than that of the music. Not really much you can do about that other than turn the volume up.

All of a sudden the volume of the videos (at least all the ones I've tested) have decreased considerably.
I don't recall changing any setting or adding any plugins, and it wont let me analyse the volume of a video.
Does anyone gave any suggestions on how I have make the video volume match the music volume?

Thanks!