Subheadlines should be inserted always via the “Headline” Block. Then you can choose the hierarchy (h2, h3, h4, …) This is important for structure and SEO. Please choose h2 then h3 then h4 etc. not jumin from h2 to h5 or starting with h5 etc.
The size can by adjusted with the options, if needed.
If an post is an add please mark that one NOT over a category, but over the custom field found at the bottom of the post in the section “layout”:
Check the “Sponsered Article” Toggle.