One of my 2 wks puppies, who is growing, thriving well, has a strange waddle, only way I can explain, is when she tries to walk, her backend waddles, like ducks do when they plump up they feathers.
I'm going to take her to the vets to get checked out, none of the others in the litter does this.
Anybody seen anything like this before??

No advice, but thinking of you and hope everything turns out ok for you both

Is the pup a bit heavier than the others?  At 2 weeks I wouldn't worry about it as it could be just the weight and of course they are not steady anyway at such a young age.

TBH - your pups must only just be up on their feet - I wouldn't worry just yet.  If at 6 weeks + it is still not walking as the others do then further investigation may be required.