Google Blocks/Poly

Hello, I did some work in Google blocks on Oculus VR and imported into Unity. When I imported it I created a mesh collider on the mesh object (the ground) and already had one set up on the player. So the player works fine and does not go through the ground. However, the stone circle that I set up as a blocker for the scene I had a lot of trouble with due to the way blocks created the rocks or due to the export (see Group image). However, to add a mesh collider I had to select each mesh under each group (taking some time) and apply it that way (MeshCollider image) . I was wondering if there is a way to apply a collider when creating the object in Google Blocks, or set it up so that I can select all of the "Groups" and apply the collider that way. I tried that but it did not work so I had to choose each and every Mesh and do it that way. Is there an easier way to approach this please? Otherwise it's going to be pretty time consuming when it comes to trees, plants and everything else. TIA