First time duck owner needs help with sick duckling...

Anyone experienced with ducklings here? We got 2 baby ducklings last week, one of which displayed difficulty using one leg a few days ago which has gotten worse, he was able to hobble around on it until yesterday, we took him for a little swim in his pool and he didn't use the bad leg at all, then when we put him back in his enclosure he just sat and now won't stand and can't walk at all :( A bit of research is pointing towards him either having a broken leg (he can't even stretch that foot out, it just stays curled up) or a niacin deficiency, I am leaning more towards a leg injury than the deficiency.. So I read most people splint their own injured ducks legs and I'm wondering if anyone has any experience with this or duck leg problems at all? He doesn't seem in pain or distressed, just can't get around much. I've read this isn't an uncommon thing to happen with ducklings so was hoping to get some advice from anyone with experience before spending a fortune visiting a vet on a public holiday..

Have not dealt with ducklings but with chicks with bad legs. We have used a splint on a few that were quite splayed.
From my experience you need to do something to recitify it now, if it goes on too long they end up dying as they struggle to get to food and water, especially when the other ones grow up.

Thanks Astrid! So the splint, do I just make the whole leg straight? Am going to separate the ducklings from the baby chicks now and give him close access to food and water, I have read that they are quite hardy and will more often than not heal themselves with some time, I really hope so as even though we've only had these guys just over a week, we're all very attached already!

With the chicks we would used a cut up straw to keep the leg straight and offer support. We would also tape that leg to the other leg with enough of an gap for standing (which you may not need to do, as we were dealing with splay)