why StyleSheet color setting changine button shape?

[vonCZ]

Hey, I'm trying to do a rather simple thing: control the color of my QPushButtons when isUp, isDown, hover, etc. I'm doing this:

myPb->setStyleSheet("QPushButton { background: rgb(230,230,230)}");

myPb->setStyleSheet("QPushButton { background: rgb(230,230,230)}");

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which works, but changes the shape & look/feel of the buttons from normal to rectangular... best explained by looking at the attached image. "Co2 Hist" and "Co2 Proj" are the buttons with the setStyleSheet functions. The others are left alone/default.

Can anyone suggest the simplest way to simply have the buttons look as they normally do, but with my own custom colors?