A little concerned about my AIO.

The other day I was playing a game and I started to hear a whining sound. It dawned on me that it was my AIO fans ramping up. Something that I haven't heard since getting the computer until now.

I noticed that the liquid temperature on the display was at 37c. The AIO is set up as having the fans pull in air on the front of the case. It was too big to mount it on the top of the case.

This is idle temperature about 30 minutes after playing a game of League of Legends. Very minimal CPU usage according to task manager (1-4%)

Now people will probably tell me that 37c is normal, but it's not my normal. I'm used to seeing liquid idle temperatures around 32-33c and during gaming 34-36c depending on if it's a CPU heavy game. But 37c at idle is causing some concern for me.

Am I overthinking it? What could be happening here?