Font inconsistency

Hello

I’m on Arch KDE Plasma. I’m running Breeze with default fonts.

There are some apps where the font looks different, here are some examples:

as you see, apps on the right have the same (even Timeshift that is running as root and it’s a gtk app), while apps on the left (QuodLibet and Qalculate) have a different font…

How can i fix this? Thanks