Journal3 blog posts are a class of pages that NitroPack does not optimize by default. Luckily, it is very easy to configure this.
- Go to the NitroPack extension: Admin > System > NitroPack.io > (Your Site)
- Find the section called Page Types > Custom Page Types
- Click on Include Page Type
- Add a page type for the route journal3/blog
You can also configure another page type for journal3/blog_posts. This should optimize your blog listing page as well.