How to resize an bones axis to be more visible?

Hi all,

I am wondering why my bones axis have suddenly changed in size. When I began modelling, everything was “normal” … Just after a while I noticed that new bones axis are barely visible.

How my bones axis should look:

How it looks when I add a new bone (it’s smaller, but I had to increase it with the bone to be visible):

I tried using “CTRL/.” to select the object’s origin and resize, but it didn’t work
I can’t find an option in the preferences that handles the object’s axis size.