Looking at the dusky pattern, it does look pretty similar. The only thing is that she (or he, I'll continue to leave a question mark on their genders

) was a chocolate duckling (so I thought she would be a chocolate) with a brown bill and brown feet. The underside of her bill is pale with some speckling. Here's some more photos. Apologies on the quality, they don't like to stand still for me in front of the camera.
Good... then, from my experience, I can confirm she is a Light Dusky duckling.
Here are some of mines, when they were almost the same age than yours :
They were born with dark brown fluff, so I even thought the first Light Dusky ducklings I had were actually
Brown Runner ducklings...
Here are some of my juveniles :
The four ducks at the center are :
- on our left : two Light Dusky Indian Runner girls,
- on our right : two Light Dusky Indian Runner boys.
They are turning in their adult colours, so their colouring here is not definitive still... but they are beautiful ducks.
The Light Dusky hens look like Trout, but without the white strips, and with dark blue wing speculum instead of just blue.
The Light Dusky drakes look like Mallard/Gray, but with more brown on them, and - again - dark blue wing speculum.
(Mines have not-so-dark blue wing speculum... or just blue/purple for one or two of them... probably because of some mutations and/or their diet?)
In my experience, it was 100% accurate after 4 weeks.
Yeah... I am just not lucky.
Last year, I had a drakelet quacking at almost 3-months-old... until his voice changed so suddenly (...took about two days, if I am remembering right?)!
This year, I have two 2-months-old ducklings - a Cayuga and a Khaki Campbell - I was so sure
were girls, since they quacked often enough...
...In fact, my Khaki Campbell duckling was
still quacking (sometimes) 1 week or so ago, and yet, has now a voice that sounds to be a mix between a quack and the so raspy voice of drakes...
Now, I
know these two are boys, since my Khaki Campbell has boys' colours... and my Cayuga actually has developped a real, raspy voice of a normal drakelet...
...Really, I can't trust voice sexing anymore...