Incorrect Font Kerning with some fonts

Some fonts have incorrect kerning in QT apps. GTK apps have correct kerning.  Some example fonts that have incorrect kerning:

• Source Sans 3
• Ubuntu
• Calibri

Example fonts that render correctly:

• Liberation Sans
• DejaVu Sans
• Roboto

I checked all my DPI settings. Xorg is manually set to 108 DPI. KDE font settings are forced to 108 DPI. ~/.config/fontconfig/fonts.conf DPI is set to 108. Xft.dpi is also set to 108.

The incorrect kerning is present in KDE UI elements. However the KDE Font Management panel renders them correctly.  Other non-KDE apps that are QT based are also affected such as VLC and Clementine.

Two of the attached screenshots show the incorrect kerning with 2 different fonts (Source Sans 3 and Ubuntu), and the third screenshot shows correct rendering of Source Sans 3 on the Font Management page.  If you look at the incorrect kerning screenshots, it appears that certain letters like "e", "o", and "u" are getting shifted to the left when they follow certain other letters like "F", "C", "x".