Change spacing for individual QWidgets in a QGridLayout

I'm working on a project that allows users to place dominoes using a 2D grid. I made a basic version using QGridLayout and QWidgets, but realized I'd like the distance between the dominoes to be variable and based on the direction it is facing.

My question is, how can I change the spacing between individual QWidgets in a QGridLayout? I've added and image for reference. (Sorry for the low quality, had to use MS Paint)