Hi I am also having problems with sick ducks we have only had them for about 2 weeks
and 1 went sick this week and passed away now another is showing the same signs ,very quiet she is eating but her feathers are looking dull we don`t think its sour crop as there is no bad smell from her bill she will follow the rest into the water but tends to stay away from the others and spends most of her time on the island .We were told their about 2 years old no eggs since we had them but we put that down to the move to a new home .
The pond has water flowing through so should be fresh although muddy when they stir it up .Any Ideas please