I recently cross fired my graphics card and my second card stays at 20% fan speed even when the temperature is at ~80 degrees Celsius. While my first graphics card goes up to 100% fan speed at that temperature.
MSI afterburner then use custom fan profile and try to synchronize GPU's.
I'm using Sapphire TRIXX and the graphics card does not go to the speed it should be at. I customized both of my graphics cards and only the first one goes to the level I set it at.
I have noticed similar issues with fan speed and overheated AMD cards in CrossFire when their ULPS system is enabled. Unfortunately, it takes a Registry setting followed by a reboot to modify the ULPS behavior.