I think they all look like drakelets, too, but I'd like to see more photos.
The best thing you can do is look at each duckling and compare them to all the others. Drakelets will be larger, they will have larger feet & legs that are wide-set. Their body will be longer from tip of the tail to the tip of the bill and they'll have a more prominent breast. They'll also begin getting caruncling sooner. Ducklets will be smaller, more compact and round, more petite, essentially, and they'll obtain their flight feathers sooner than drakelets although this is a late finding.
If you can post photos of them standing, in profile, it's easier to give a good guess. It's a 'whole picture' type of thing. You have to be able to compare each of the traits I listed above to the other ducklings and of course, if there are birds of different ages then that will make guessing all the more difficult if not impossible to tell.