Third Monitor Shuts Down

Hi. I'm having a recurring problem with a third monitor. I have an Nvidia GeForce GT 705 and onboard Intel HD Graphics 4600. All my monitors are LG W2243S. Originally on Windows 8.1, I activated the onboard graphics and ran 4 monitors for several months. I upgraded to windows 10 and ran the 4 monitors for about 6 weeks and then problems started. Monitor 3 would shut down. If there was a window open in full screen it would stay on much longer. I swapped out the monitors and ports but always #3 had the problem. I moved the computer to a different room where only three monitors were practical. They worked fine for about 6 weeks. Monitor 3 has started playing up again. The system is all up to date. I have even tried reinstalling older drivers to no avail. Any ideas?