It took me some time to figure out how to change case from a heading style title case to normal lower case with my current theme.
The template that came with the theme had Title Case and Heading Styles loaded. No options within the box to change from the Heading Style (title case) to a regular (non-heading) style within the Beaver Builder pre-loaded boxes.
I eventually tried grabbing a new text box and found that to be the thing to do.
Copy the text from the original box, and paste it into the new text box you dragged over. Then you can click on Style tab, next on Style and Spacing. Then click on the normal tab. This will change text you copied from Title Case to normal lowercase.
Click Save, Done, Publish in this order and you're changes will be live.