We have 2x broody chickens that were sat on non-fertile eggs and a duck laying fertile eggs but not sitting on them. We were told to put the duck eggs under the broody chickens which we have done, but a duckling has hatched from each chicken but when we have noticed them they are already dead. Other chickens are loose in the coope with the broody chickens - would they be the one's attacking the ducklings? really not sure why they are dying... or would it be the broody chickens not accepting the ducklings? can anyone help?

I am sure I have heard of hens hatching duck eggs. I don't know why the ducklings are dying. Maybe you should try to incubate the duck eggs. At least you could control the ducklings better when they hatch.

Anyhow, good luck what ever you do.  I hope you get some to survive.