Unpleasant change in fonts

[Jonathan Ryshpan]

I have made some change to my system which has affected the fonts used
for window names and the names of thumbnails in Digikam, possibly other
situations.  The fonts are very small and don't display certain
characters, in particular č, œ, etc.  These fonts resist change by using
either the KDE ControlCenter->Appearance&Themes->Fonts tool or the Gnome
FontPreferences tool.

I have no idea what caused this; the only change I've made to the font
system lately is to install fonts-chinese and wqy-bitmap-fonts (also
Chinese fonts).

Any ideas what's going on or how to fix it?

Thanks - jon