Please help! Sick Duckling - Can't keep head up - Updated

[dd62]

Hello all. I have a problem and hope some one can help. There were some new ducklings in our yard today and I noticed one just standing in the rain not moving. The rest of the ducklings and mother left it. I have since brought him insided and I think he is sick. He cant seem to keep his head up, it keeps leaning to the side. and he cant walk right either. He has not pooped which probably means he hasnt eaten. I have tried to get him to eat but he wouldn't. I even tried placing food in his mouth but he spits it out. Does anyone know whats wrong with him? Anything I can do to save him? i actually found a duckling like this in the spring and the next morning he died, so I would like to try and help him. It is a muscovy duck, and we live in south Florida. I think he's just a couple of days old if that. Thanks In Advance.

Updated: So last night after dark I looked out side and found two ducklings laying on there sides soaking wet. When I brought them in side and dried them off I realized they had the same thing wrong as the first. Very weak, Head falling to the side not staying straight, and not eating or drinking. I also walked around and found a dead one. The three that I had have all died. I am very worried with what could have caused this. There were about 20 ducklings yesterday and I'm scared that I am going to walk outside and find them all dead. Does any one have any idea what could have happened? What I can do to help the duckling if I happen to find another one with the same condition?

Thanks