A bit of a hack, but you could wire the button signals from 3 PBs together to a single button, then they would switch at the same time.
The Pixel Lights app was designed for houses, but will work with any network of Pixelblazes. It works like Firestorm, and activates all patterns with the same name. To have it run something different on each PB, you’d have to have different patterns on each but name them the same.