Monitor(s) is Dark

Hi,
I noticed that we have had our Optiquest Q51 monitors suddenly start going dark one by one. We have 5 of them, about 2 months ago someone's went dark. I tried a new video card just incase but it was still dark. It is dark when booting up, dark in DOS and dark in Windows. On the monitor I tried to turn the brightness all the way up and the contrast, etc. I hit degauss. I messed with every darkness/brightness control on the monitor.
So is this the monitors going bad? The monitors are a little over 3 years old. The only reason i ask is this too much of a coincidence that an additional 2 monitors are going bad at the same time.
Any thoughts? I am just leary that 3 monitors would start going bad at the same time.

Thanks in advance,
D

Yes, they could all be failing. A few years ago I had a client with three Hitachi 17" monitors all go dark within a few weeks of each other. One was worse than the other two and all were still somewhat usable but still noticably dark.

Most likely the monitors have lost a color tube (magenta or yellow), probably due to a manufacturing or design defect. Lost of a color tube is common among old monitors but I have also seen a few rare cases where a faulty color tube in a particular model caused a bunch to go out at one time.