Unable to override page background without important

Hi

I was using .page-id-xxx .inside-article { to override default page background but seems something has changed of late. I saw today that my live site was looking strange and i went through my custom css thinking i did a mistake somewhere but no.

Adding !important to background property works. Should i be looking for the fault somewhere else?

Thanks !

Edit: Only that that changed in my install is two plugins,Autoptimize and Wp Super Cache.