subdued theme question

[lang-server 2]

This is a trivial question. Does anyone know how to eliminate the "shadowed" box around the home page icons using the subdued theme. If you look at the attached, you will see a faint rectangular background around the "non-selected" icon. The current selected icon doesn't show the box. It's not the " dim focus frame" option, that actually does dim the background, but doesn't fully remove it.

 

Thanks