Lazy duckling or am I missing something?

[KCNC06]

Alrighty, so, I've got a duckling who is starting to confuse me. Or at least make me wonder if I should be concerned. I have 3 that hatched on October 24 - Sassafras, Percy and Backwards Betty (Betty was breech and hatched from the pointy end of her egg). Sassafras and Betty's voices are already starting to change, I hear that little honk-like quack every so often.
Anyway. Sassafras was the first to hatch and she's the one I'm confused about. When they first started walking around she seemed a little lazier than the others. I can't see any physical differences, nothing looks or feels wrong with her legs. They've been getting Mazuri waterfowl starter from the beginning and I give them a packet of durvet probiotics in their water every other day. I've also been giving them a sprinkle of fortified nutritional yeast on their food at least 2x a week to make sure they're getting extra niacin even though the Mazuri food should have enough for them. Sassy still lays down more often than her siblings and if we're sitting on the floor is much more likely to climb onto someone's leg and lay down than the others. I've also started giving them a squirt of B-Complex on treats once a day just in case she's somehow not getting enough from the Mazuri starter and nutritional yeast. Though, it seems weird that it would be a niacin deficiency since this behavior started when she was about 2 or 3 days old and she's getting all the same stuff as her siblings. Is it possible that she's just more of a snuggler than her siblings? She did get more one on one human attention her first 24-36ish hours since the other two hatched a good 18 or more hours after her. I don't want to overdose her, or them, on niacin if she's just lazy or a cuddler. Is there a clear way to tell the difference between niacin deficiency and "lazy"? (I did read the sticky post about niacin deficiency but I don't think there was much there that folks here, and in other duck groups, have already taught me. I've had ducks for a good 10+ yrs and have had 4 house ducks for 2+ yrs now so duck care isn't new. Sassy just seems a little different.)
I can try to get video of them later, they're napping now, but she doesn't look different when she's walking around. They're all fairly clumsy looking when they're walking around but baby ducks always look a little clumsy. Especially when they get into this stage where they're growing fast and look like gangly teenagers. Her legs don't look bowed, don't appear to have any trouble staying under her, she climbs people, pillows, dogs, whatever else like a tiny mountain goat. She just decides to lay down when she gets to wherever she's going. Am I worrying for nothing?

 

[ruthhope]

What sort of ducks are your three ducklings?

I have found that juvenile and adult muscovies are much less athletic than Pekins. My son's Pekins do rest sitting down but spend a lot of time on their feet exploring and come running up when anyone goes into the back yard. My muscovies that are the same age are great lazy lumps. They do waddle up if I go into the back yard but running isn't in their habit. They do spend a little time foraging -- but not much. They prefer sitting around watching the day go by!. I don't know it the muscovy I raised in a brooder in my home was more or less active than my son's Pekins when they were in the brooder in his home: I didn't think about it at the time. But I suspect my muscovy was less active as his three were frenetic running back and forth between feed and water -- every time one had the idea, the other two were imprinted to follow.

However, even within breeds, some will likely be more active than others. For muscovies, males are more likely to sit down lazily than females.

 

[Crazy Maizie]

I'd guess your lazy duckling is a male. Your feeding appropriately so I doubt it's about deficiencies.
Post a video so we can see how lazy. Maybe we will notice something else going on.

 

[Quatie]

I have had some ducklings be a bit more lazy. I give weaker ducklings scrambled duck eggs to give them extra nutrients. But as long as they are eating and drinking plenty, I wouldn't worry too much.

I had one runner that was especially small. She really didn't want to move much, even when encouraged, until she moved outside and had to keep up with the other ducklings. Her legs started to really strengthen and she took off.

One of my Saxony ducklings would pig out, eating a ton, and she was always sleeping. But some breeds do seem to be more active than others. My khaki Campbells were by far the most active ducklings I have ever had.