Maybe genetic? Hard to say but if you can afford it maybe an avian vet would be worth a try. You do know crested ducks can have neurological problems?WEll I dont see any leg problems in any of the 20+ ducks I have? they are normal and strait? The older ducks never had any problems and this group is younger and about 8 weeks and I have 15 in that group both groups were fed and treated the same? the first runner duck I kept up for 24 hours and then she seemed fine...yeasterday another crested duck started have seizures!same group but not as bad as the runner duck but still! so she is up now...I have not gone to check on her this morning