To be more helpful, more than just the DA change that day needs to be considered. The temp, humidity, and just to be sure the the barometric pressure for each run. I have seen what happens when the temp goes down and the relative humidity goes up and the ET doesn't change. And the same for morning til afternoon when the temp goes up, but the relative humidity goes down. You saw a 1200 ft DA swing on the same day, that is a lot.

Also if the car did anything different on a run. Spin, moved side to side (driver steer), etc.