Some filings are normal. I wouldn't get too excited about it. What I would do is grab each turtle, one by one... and rock them fore/aft to check for slop in the bearing. If you find one that's loose... replace it. Those are pretty easy to change. 4 bolts in the turtle shell then 4 more to remove the module from the bar. You can either change the module for the appropriate Kuhn part or buy a new bearing from Deere.