we have two 2 mallard ducklings. they were both healthy, until yesterday. the smaller of the 2 can no longer walk. he/she can not put weight on her legs. she belly crawls to the food and water. she does eat and drink, but no longer walks. has anyone seen this before, or have any suggestions. we love this little duck and walking or no walking she will always have a home. we just want to make it a happy one for her.