That fast of leak almost certainly in the rear line under the left front seat. There is a design defect that causes this failure.

Mine blew out dramatically from a deer related fast stop. The panel well hold a lot of fluid before it drips out but usually it will puddle by the time the low fluid light comes on. I think your leak is slow enough your are just leaving drips along the way

__________________
2011 E70 • N55 (me)
2012 E70 • N63 (wife)