If you look at the text editor instead of visual in the first post in wp-admin you can see a style inside the paragraphs in <span> elements:
style=”font-family:’Times New Roman’, ‘serif’;”
In the older posts there’s a style:
style=”font-size:12pt;font-family:’Times New Roman’, ‘serif’;”
The difference between these two is that the first uses font-size: 14px and second a size of 12pt, you could try defining the font size to 12 in Word and then copy it again and update the post.
You could also paste the font-size: 12pt to every <span> element in your post, but that takes more effort since you have to paste to every paragraph in the post.
