Why are my upper and lower left premolar moving? Appreciate all answers! Thank you. (Photos)

I had braces around 7 to 8 years ago. I am 23 years old now. I had partially impacted lower 3rd molars and recurrent pericoronitis so I had them extracted.Prior the extraction, I noticed my lower left second premolar had shifted lingually.My orthodontist also suggested there might be movement because of the lower thirds. However, now that they're out I'm waiting for the tooth to go back to position.However just yesterday I noticed that my upper left premolar has also shifted lingually a little.