Custom font throws off paragraph formatting

I just installed a custom font on a blog for someone. The font is Deja Vu Sans Light. I changed the font in the CSS to be the default font. It works fine but it throws off the paragraph formatting and now the users posts are all one paragraph. If I open a post, change the formatting to H4 (or probably any H) it looks fine. How do I resolve this without the user having to change it to H4 every time she writes a post?

I apologize in advance if this is a question that has already been asked. I did a quick search and didn’t see anything relevant.

The blog is https://donnajones.org/blog