Level 16501 Problem

I am at Level 16501 and there is a bit of a problem. To clear the Level you need to clear 4 end of track stars. ( Not sure what they are called) 125 yellow drops and 25 bubbles. The source of the yellow drops are the check mark circles. To clear the end of track, there are 4 yellow drop guards where you need 5 yellow drop hits to clear. I cleared 3 of them, but after you complete all 125 yellow drop task, the check mark circles stop turning into yellow drops. There is no way to clear the yellow drop guard since no additional yellow drops are generated. It's really not fair