KDE 5 Plasma: Blurry fonts in KDE specific applications

[philip]

I just upgraded from KDE 4 to KDE 5 Plasma. Almost everything worked fine until I tried another Look and Feel (Oxygen) and changed fonts. When I wanted to go back to the default Look and Feel (Breeze) and fonts two significant, persistent problems remain:

1. The fonts in KDE specific application, like widgets, the panel clock, Dolphin and entries in the KDE Application menu have a green tint and are fuzzy

2. The font Noto Sans (defualt in Breeze) is not available in the Fixed width menu any more. There are only a few fonts left in the Fixed width font options

There seems to be no way to revert back back to the default fonts.

I created a new user to see if the problem is related to my user name. But the problem persist even for a new user.

I have tried to enable anti-aliasing in the Font System settings and forcing fonts DPI to 96. None of this helped.

Fonts in non-KDE applications, like Firefox, Libre Office etc are not affected by the problem.

Here is a picture of what the fonts in Dolphin looks like http://picpaste.com/pics/blurry_fonts_kde5-kVZ9nHkr.1470152117.png

Does anyone know how the affected fonts are generated and rendered (e.g. the fonts of the systenm clock and the ones in Dolphin, as can be seen in the screenshot)
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/Phil