Are you using PrecisionX or MSI Afterburner for a custom fan profile?

It helps keep the temps down so your video board doesn't throttle the core clocks. When your video board reaches a certain temperature it starts to lower the core clock rate to protect itself from damage. I prefer MSI Afterburner over PrecisionX for personal reasons. They will both do the same things. Here is the custom fan profile that I used with my GTX-680 video boards that would throttle at 70°C:
 

 

It should work pretty good. My 680 SLI setup rarley went over 68°. Here is a screenshot:
 

 

What games are you playing? I'm having some issues with Far Cry 4 right now.

try driver 344.60 with 5.25 precision X16 and set the fans and don't forget to click apply. don't close the precissionx then run your game and listen for the fans to ramp up. if you hear the fans speed up then it should work. set the fans at 100% at 40 degrees just to test the settings then go back in and reset the fans to your like. try that

Here is what I would recommend...
 
#1 Perform a clean boot of windows.
 
#2 Perform a clean installation of video drivers...

1. Uninstall Precision X/Afterburner if installed, make sure to select "no" to saving profiles when asked. Reboot the machine.
2. Download & save 344.75 driver to your desktop. 
3. Run the 344.75 graphics installer located on your desktop.
4. Select custom advanced install, under custom installation options uncheck all options except physx system software, if you are using audio over HDMI please select the HD Audio driver, if you have a 3D capable monitor and would like to use 3D at some point select the 3D Vision driver also, check mark perform clean install, then click next to install the driver, reboot when asked.
5. Re-install Precision X/Afterburner if you want.

 
#3 Disable XMP & setup your RAM manually inside the BIOS. The frequency, timings & voltage set inside the BIOS should match the JEDEC stickers on the sides of your RAM modules.

 
#4 Test and report back with your results. 
 

Well if I configure MSI afterburner to crank the fans at 100% before I start a game I have zero problems. Looks like I'll have to water cool this rig because the fans sound like a turbine engine.

Depending on how long you've owned your video boards and where your PC sits, on the floor with lots of dust or on a table or desk, it might be time to remove the cover and clean the dust from the heatsink fins. After removing the cover it would be easy to replace the TIM on the GPU itself. If you don't feel comfortable replacing the TIM you could get a local PC repair shop to do it for you. If you're not familiar with the limits of tightening small scews you could easily break one off. I used MX-4 for my TIM. You could also RMA your video boards one at a time for excessive temperature problem but that's up to you. Here is a video on how to replace the TIM on a GTX-780 Titan Black. I never replaced the thermal pads but never needed to since I wasn't replacing my air cooler for a water block like in the video but you get the idea how involved it is: