I noticed that we no longer had a retro-reflected green beam even though we were aligned onto the QPDs. TMSX was as follows: PIT: -103, YAW: -297. In order to get the retro-reflected beam back, I had to move TMSX to: PIT: 13. YAW: -323. I am not sure what would have caused the offset to drift so much. I have turned the clean room fans back ON to see if this caused a drift in anything.