I had the same thing until the latest release. Since 8.1.5 both fonts and icons looked extremely pixelated/low res. Could barely read them. Latest Healbot version fixed this.
However, if you still use an older version, I found the following workaround:
Go to System>Advanced and click the checkbox "UI Scale" once and press "Apply". Uncheck the box again and close the window. Miraculously fonts and icons were smooth and crisp again. Sadly you had to do this all the time after relogging.