Site text went bold suddenly!

Hello!
I run is some troubles today. After making a new post on my site yesterday, today i find that almost all the text on my site is bold. Except of the italic one. This happens no matter of the browser used. Also on mobile the text looks normal.
Anyone has any clue why this happened and how to fix it??
Thank you!
Note: when i started using this theme i made some modification to it and, for not losing them, i blocked the theme update. I know is not the best way but is most suited to my knowledge and it worked fine till today. So updating the theme is not a solution for me.

The page I need help with: [log in to see the link]