My Duck, who is about five weeks old has been slowly been acting more and more strange. Now its neck will not stretch out all the way so it cannot clean itself. It also has problems walking, it trips and falls, he has no balance he can fall on his back and can't get up on his own. He also cannot swim anymore he just sits in the pond doing nothing. He has other troubles in flapping wings, his flaps are small and look awkward. My other pekin of the same age has no problem with these activities. He just keeps getting worse, what should I do?