Okay, I will be the direct meanie in this thread because it needs one.
Goat Walker - look at the pictures you posted...those babies are not healthy and of course they are peeping they are in distress! The feet of the black duckie are not functioning and look malforned, there is an obvious problem with their spine and the necks.
You are not looking at a vitamin deficiency. You need to cull those poor babies.
The link posted for reference is useless! It does not discuss DUCKS! That is about incubation and regardless of why this has happened the fact is that it has happened!
Do the right thing for them. A sharp pair of scissors, a ziploc bag and snip the head off and it is over. To see them like that is heartbreaking and I cannot understand why you would want to put them through it.