Need some help with button look and feel

I am working on my first plugin and I can't for the life of me figure out why my buttons look and feel as they should when I am using the Darcula theme but when I switch to IntelliJ or Windows they look completely different.  I am obviously missing something. Can anyone lend a hand? I have tried looking at the IDEA source code and plugins in community but was coming up short in this regard.

At the moment the buttons are initialized with these settings:

setBorder(null);
setBorderPainted(false);
setBackground(null);
setOpaque(false);
setContentAreaFilled(false);
setIcon(GenoaIcons.closeFile);
setRolloverIcon(GenoaIcons.closeFileHover);
setToolTipText("Close");