One change per upload
Pick the video that is closest to working. Move the best line to the front. Delete the section where the graph falls off a ledge. Publish a sibling video, not a totally new idea, so you can see if the edit was the difference.
Average view duration and completion rate tell you more than views. A short video with a high completion rate is a format. A long video people abandon at 20% is a title that overpromised or an opening that stalled.