You can press the eye icon to enable debug on collision to see in the first place collisions are reacting to eachother.
You can also increase collision radius, since there is drag an early collision can be usefull. Since there is a drag you can lower drag and collision friction so it has a better visible effect and you can add a force with impact normal.
Drag can physically prevent you seeing the effects so you have to manage that, you can make hanging particles without drag too.
