First, I cant see the video due to being on a government computer but have you tried placing the drop checker in different areas of your tank to see if they are different readings in different areas? If not, I would start there. It could be your flow that is preventing that area from getting the proper amount of CO2. See what happens and let us now. Remember it takes a couple hours for the drop checker fluid to change, so any changes you make in CO2 rate or flow, give a few hours to see and changes before making another change etc...