Font inconsistencies within single post?

I apologize if it’s been answered, but I didn’t see it… I have had the same problem several times and my various attempts to solve it have not worked. I have a bunch of posts where, regardless of how consistent it looks in the post editing pane, and no matter what I do to rectify, the post ends up with varying font sizes. One thing- I have cut and pasted from elsewhere, but they’re all one font and one size, and there seems to be no rhyme or reason (though I’m sure I’ve just failed to detect it) as to why one post is this way and another isn’t. I’m building them all the same. Any ideas? Any advice is greatly appreciated. Thanks everybody!
if an example helps, please try this:

https://footballsickness.com/brownsnote/2010/04/27/dawg-draft-2010/

or

https://footballsickness.com/ponsky/2010/06/25/breakout-2010/