If you change ".page-content p", and forget to change ".page-content p + p", then you get the effect on the screenshot. You have to change them to have the same values at the end of the line. If not "12px", any other value, but it has to be the same at the end of both lines.
It is the same spacing for me as well when I view the page. That said, I believe I have identified the issue. NZ9002, you appear to be using OasisRevived in your global CSS/JS. It appears that the CSS corrections have not yet been updated for the newer global CSS that Fandom released a week or two ago.