2.6.1 has tiny font, is this breaking custom css?

I noticed once I got my 2.6.1 working that all the font size is tiny, when I made my theme I used some custom css to re-size the font way before I moved to 2.6.1, I also found this thread

Upgrade to 2.6.1 No Longer Loads Custom CSS

But no replies, did custom css/themes change?

The default font size if for ants.

https://piratemc.com/forums/