I am wondering, why is the same icon blurry on iOS 8.1, but sharp on iOS 7.1.
Please consider this two images:
I finally found solution. I am using Apache Cordova project - all icon formats are set in config.xml. At first build, icons were all OK. But icon design had been changed, so I had to change all icon source files. After this change, the blurry icons appeared at iOS 8 devices. I solved this using Xcode and its project settings of App Icons and Launch Images. I tried to manually drag and drop icon source files into the App icon list in Xcode. And after that, all icons are OK again. It seems to some issue connected with Apache Cordova config.xml settings of icon files.