Twenty Sixteen – Padding

I recently changed my theme from Genesis to Twenty Sixteen. One of the things I like about Twenty Sixteen is that the <P> text is indented relative to the <H> text, meaning there is left-padding in the <P> and the body text is narrow. However, my old posts didn’t change and they don’t have this left-padding, but are aligned with the <H> texts. Therefore, the body text is much wider than should be with this theme. Any way to fix this without reuploading every post?

Please assist!

This is my website: https://objectivebinaryoptions.com