Yeah they're doing a fast controlled descent. Whether it's a low battery failsafe or a response to loss of control signal isn't clear but they're doing their best to land.

The first few look precipitous but you don't see them approach the ground, later in the video you see one that's coming down very fast and then makes a reasonable effort to brake when it gets near the ground.

Edit: Most of them are doing a fast controlled descent, a few seem to have just powered off and become rocks.