V-Core 500. X Axis

Here is my height map. I have watched the video and didnt see my specific mesh as an example. I spent a lot of time making sure the frame was true and square. As you can see the lines between the three axis points are in the same plane but the rear corners seem to sag. there is nothing loaded on the plate corners so i am guessing it is the beds own weight. is there a remedy for this? I let the system warm up and then losened the X-Axis and retightened after and the mesh didn't change. I didn't do the same with the Y-Axis but i see that maybe that could help? I understand i could fill the corners with kapton tape as a last resort but wanted to check in first.