I had 2 appleyard ducks,2 Aylesbury ducks & a drake-i have had an appleyard go off her legs for some reason & die, & now i have an aylesbury duck go off her legs-im hoping shes not going to die! They are all roughly the same age,a couple of years old,but why have they gone off their legs ??? any ideas anyone? What could it be? Hip problem?