Monitors Won't Turn Off?!

Hi all, whenever I lock my Windows 8 PC using the WindowsKey + L the PC will lock but the monitors connected to it won’t turn off even though I’ve set them to turn off after 5minutes of inactivity. The only reason i can think of is that the Windows 8 PC is running TeamViewer.

How can I tell my monitors to turn off so I can save power?

Thanks for any help!