You indeed have some white background color being substituted but only on phone, not tablet, and not when we shrink the desktop to phone size.
that last part make me think, that unless you have added Custom CSS rule using mobile OS classes to create the rules, it is not coming from the theme.
I would start by deactivating ALL non weaver plugin and see if the problem disappear, if it does , reactivate one by one to find the culprit.
You may have some mobile option activated in some plugin, interfering