Hello Terry. I guess the other experts will also offer you a solution but when I had the same problem that way I minimised it was by duplication the track so you then have two tracks. Go to the frame on the Upper track to where the problem blobs starts and Slice it and remove all of the part before that section and then go to the end of the problem bit and remove all of the bits after that. So you may have three or four small sections on the top track.
So you are now left with a complete second track and a top track when the problem area is directly over the in sync with the second track.
The on the Top track, using the Pan/Crop I masked out a very small section of ( in your case Sky ) just to either the left or right of the problem area depending on which area it like the area with the problem.
The using the Feather with the mask tools just feather the edge to is it not sharp. Then I moved the top track using the Track motion so that the masked cloud nice bit on the top track covers over the blobs on the second track.
As both tracks are in sync then the mask will always cover the blobs. Of course you will get some part where you will have to do a different mask area like when the blob goes from sky to another different area like rock.
Whilst this is not exact science for me I got away with it..
I also hope others will help you with some ideas