From what we can see in the admin change history, it looks like what changed was the optimization goals settings. On the 24th, it looks like you went from Balanced to Revenue, and then 10 hours later switched back to Balanced. Then on the 26th, you changed it to User Experience focused.
And then as you noted, from that day onwards, the settings for that started to jump between the 3 settings. While we can't say that's the definite answer that contributed to that bump in earnings, that is the most significant change we can see happening from our side.