There is 100mg per 1mL which they are recieving once per day. I understand that I am a beginner and really want what’s best for my ducks, if I thought I was doing all that I can I would not have returned to this thread. I’m sorry if I have said something to upset you, i’ve had many people praise the liquid b complex to me and don’t want to stop administering it if it could really help them like it has helped so many others. There is no reason to get rude ):
		
		
	 
The response was a little bit curt, but I’ll agree that it IS possible that some amount of deformity may be irreversible.  You’re catching it early so there’s a better chance that you can correct the issue OR at least prevent it from getting worse.  While straight niacin may be a better or more direct approach, I wouldn’t go so far as to say that the B Complex isn’t a suitable substitute.  As you’ve mentioned, many others have used it with good results.  The presence of other B Vitamins in the supplement really is a different topic of discussion and not directly related to your current dilemma.  There might be some concern of giving them too much of things unnecessarily (I myself haven’t researched it enough to comment), but again that’s sort of besides the point here.
I’ll share my beginner duck experience with you for whatever it’s worth -
I got four Pekin ducklings from Meyer Hatchery after doing what at the time seemed like adequate research beforehand.  About two weeks in, I noticed one was sitting more than the others.  Still eating and getting around and happy, but sort of seemed almost lazy.  And she was growing a little bit slower than her brother and sisters.
I came on here and found out that I should be supplementing her niacin.  I was feeding Purina Duck Starter Crumbles, which reported the correct amount of niacin (55mg/k which translates to some other mg count per lb of food, which is an important distinction btw...you can search it out - I can’t remember at the moment).  I had read Isaac 0’s post about niacin needs, but I somehow missed the part where he said that Pekins have higher requirements, around 70mg/k.  So, I went and got the B Complex and some brewer’s yeast.
As I mentioned, I had a heck of a time getting her to take the B.  She shook her head violently when I tried to give it orally and fought me like crazy.  I’m sure she wasn’t getting enough because it was coming out the other side of her beak and getting all over me.  I tried endless types of treats, but even separating her made it hard to get her to take the treats, since she was so upset about not being with the others.
I let it deter me.  I’d still try, but I let it go on longer than I should have, believing it would correct itself or I’d still have time to correct it because she was still young.
So at about week 3 1/2, she was sitting more and it was getting worse.  I came across the Metzer article referenced above, where he basically says “damage done is done”.  I freaked out and set out to make sure she got every bit of her requirement, no matter what.  
For me, the easiest was to do it in the morning after I cleaned their house. I’d put the other theee back and leave her in the other container. I’d give her mealworms with the B on top, a little water, and even some crumbles in it too. I doubled the dose. Inevitably she wasn’t getting the full dose otherwise, and with an extremely low possibility of overdose, I thought it was worth it.
At 8 weeks, I took her to the vet.  She was walking poorly, flipping her feet over and standing on them, and it was rough.  The vet said I had to decide about her quality of life.  I don’t actually know if it was a niacin deficiency, or an unknown poorly healed injury, or a birth defect.  Whatever it was, damage done.
 My husband and I talked it over daily.  We moved them into their outdoor home, and she loved it.  She seemed happy except for the walking.  I was going to see my family out of state and we agreed we’d make a decision when I got back. 
She’s 14 weeks now and walks really funny, stiff-legged like she’s marching in the German army.  Her legs have gotten much stronger, though, and although it looks weird, she gets around fine and hardly ever trips on her feet.  She’s always going to be a little bit of a “special needs” duck, but she is happy and her flock mates come back for her when she’s a little behind them in the yard.  I’m so happy that we have her time.
ALL this to say, stick with what you’re doing and don’t be deterred.  Maybe increase the niacin?  Idk, that’s your personal decision and I’m no expert.  The damage could partially be done, but you’ll save her from more damage by sticking to it.  Exercise is HUGE!  They’re young yet but any chance to get out of the brooder and walk/swim does wonders for developing bodies.  And even if she has a forever different walk, that’s not necessarily condemning her to a bad life at all.  My Annie is proof of that.  Birds can be incredibly resilient even with how delicate they are.