Alexander C. answered 06/01/19
Video Production Specialist with 15+ years experience
If you are using Adobe Premiere, you can drag the audio compressor effect onto all audio tracks at once, and set it to the level you want. A compression ratio of 3:1 would be less aggressive and would level everything out. You may have to raise the db a bit to get it back to -6 db average.
If you are using something else as a video editing software, what about combining all of your edited video tracks into one long timeline project, and then export the entire mp3 track? Then use audacity, a free audio editing software, to do the same compression I described above. Then bring it back into your editor, and then export each segment of the timeline individually as needed for each video.