I'm so sorry to hear this *BIG HUGS*
I am glad the charcoal worked. But that means your ducks ate something toxic, and you'll have to figure out what it was and remove it.
You may not feel like it right now, but you'll need to get a companion for your duck (and chicken). Being flock animals...
Get them to eat activated charcoal. It will absorb toxins. And it won't hurt them if it isn't toxins. From your other posts, it sounds like you're in Australia, which to us northerners is known as the Land That Wants To Kill You In Any Way Possible.