Have you installed the WM hub as stated in your
manual(page 31)? If so then only one of your fans wil report teh PWM signalling back to the motherboard and thus the RPM will be reflected as such.
Using this as a guideline;
It's not physically/electrically possible to control all your fans rpm's(individually) with only one header off the motherboard. Can you state with a pic how you've connect the fans to the hub and in turn the motherboard?