How come my font sizes appear smaller in my images page?

So I am trying to figure out why the font sizes on my header title, nav, and subtitles appear smaller in my third page where I dispaly five images. The titles are in H1, subtitles, h2, and footer h6 font sizes. What caused my font sizes to change slightly smaller when I added my five images? I provided the code for the third page only. Pages 1 and 2 are fine.

Both pages 1 and 2 are normal as they are. Header title is h1, subtitles are h2, and footer is h6.

Hi! To make help possible, show your code, please.