I think they are naval star shells and artillery smoke shells.
That was my guess. Flares to illuminate the scene. I guess they could start a fire, but urban renewal is needed in any case in the area.
I am with you, the slow descent of the ‘stars’ does not look like a munition designed to destroy or ignite something. And in the one photo, the ‘airburst’ is too high for proper effect ... unless of course the fuse was improperly set.
I have no background in arty, so I am looking for FReepers in the know to ‘splain these shots. Some of our pilots may know as well.