Font-weight 400 not showing properly

Does anyone else have this problem where the font-weight regular and medium both show 500 instead of 400 and 500 respectively? Any font that I use which has 200, 300, 400, 500, 600, 700, 800 ,900 does not show 400 as regular. This must be a bug or error in the text module. Why have both in the text module if it doesn't apply different weights?

Cannot believe no searches come up in Google with this issue except one form some forum that isn't any help.

This has been bugging me for a while and I can't seem to find a fix except for defining all my p tags in css, which limits all my <p> with that styling and all sorts of other problems.

Thank you to anyone who has found a fix for this.