The plot below shows that most of the SpaceX Starlink satellites have moved from circa 450 km to circa 550 kilometers already, using their argon-based ion engines.
A few, along with four unidentified debris objects have remained at 450 km.
But one has moved down to 390 km.
Since it's only one object and six have remained around 450 km, it makes me wonder if this is active, propulsive deorbiting, or if this is how fast these big flat satellites would decay without propulsion or attitude control.
Question: Is SpaceX propulsively deorbiting a Starlink satellite already?