we use nightvision for admin and lately when activated daytime is always foggy

Do you modify any of the weather.* vars or load a specific weather pattern with weather.load?

no all should be rust standard never changed any convars

I'm not seeing any fog on my end, something on your server must be changing weather vars, it is the only thing I can think of that would cause this. You could try and compare the weather report from the server and your client in the F1 console with sv weather.report and weather.report. 

weather.report should always report a clear day with no fog when NightVision is active. If fog is not 0 when checking the report run sv weather.fog 0, this overrides the fog var and will tell you if a configuration or plugin is causing the fog to appear.

https://imgur.com/a/QMaMrBF

just checked the report as you said and....

Clear    | Clear   | Clear   
previous | current | up next 

Wind 0
Rain 0
Thunder 0
Rainbow 0
RayleighMultiplier 1
MieMultiplier 1
Brightness 1
Contrast 1.2
Directionality 0.9
Fogginess 0
Size 2
Opacity 1
Coverage 0
Sharpness 0
Coloring 1
Attenuation 0.15
Saturation 1
Scattering 1
Brightness 1​

and now its not foggy . weird ..... im just going to name this server oops and mark this solved