It's only dropping by like 200 rpms but it doesnt make sense that the more load the less fan speed. The second i close all apps the fan speed increases. I have it set manually to 65%
I recently updated to the latest verison of msi afterburner and seems I'm having similar issues as you.
I have 550 ti card when I start msi and set my fan speed to around 71% 33?? Rpm. Then start my game when game loads my fan speed will drop to around 3000 rpm.
Not sure if this is msi related or psu I am going to try investigate the issue.
This wasn't happening till update of msi afterburner.