I think your ducklings may have passed the point of imprinting with you, they are bonded with each other...like my first brood did...they thought I was the boogeyman when I cleaned their cage, gave them food or changed their water... ugh!  The second brood I had only 3... these babies are way better, I actually have 1 gosling and 2 ducks... the buff duck is practically independant, the indian runner seems confused most of the time...but my gosling, she is 100 percent my follower...and their leader, so that makes everything work well. I walk somewhere-she follows, they follow her... it works. 
I feel for you, I wish I would have been able to bond better with my first ducks...they are ok now, they don't run too far away from me now and are less skiddish at 12 weeks. Once they grow up, they will identify you with good things such as clean water, food and treats...they will come around if you maintain routine and a calm manor.