You *may* have a power issue. However, surge protectors are limited in that they can protect within their rating only once. They will continue to work in many cases as a simple power strip then after. Better surge protector if a power spike, etc., quit and/or have a telltale LED that changes color or goes out. if likely a surge problem, replace surge protection. Only a power monitoring setup that records power usage gets a hint of a real problem there.
The other side is the video signal got hosed for whatever reason. The video card/port is hosed. Either replace the video card or buy a video card in place of a video port. If you haven't, try using the old monitors in another system, though they could pose a problem elsewhere, assume risk here.
Last, a 4yr. old monitor can simply fail on its own. If the replacement was similar age, that too can succumb. if you've problems with the video output, aged monitors simply make it more known. I thought the monitor cable is at fault that's rare, otherwise use another cable.
After 4 years of use, my son's computer monitor had a sudden flash- and lost the picture. Now it will not display a picture and if you push the power button, you hear a clicking noise like something is trying to work but can't.
So we get another monitor and 5 days in, the same thing has happened again.
Could it be the cable between the monitor and computer? Or maybe a faulty surge protector?