Inconsistent font in flipcards in Rise

Hi everyone reviewing my rise course is commenting that my fonts are different throughout the course. Yet it can't be because I've set the paragraph font as Open Sans in the course style and the paragraph option is selected in the drop down of the wizzywig editor. Yet they definitely look different. I've tried changing the size and it's not solving it. It's mainly in the flip card interaction. Also tabs. I do have a different font for headers - Droid Serif - but even if I change that to Open Sans too, it isn't solving my problem. I've screengrabbed one example. Can you help, please?