We had six duckings about two months old. We have a kiddie pool pond, but also give them fresh water and food daily. We had one duckling die two days ago. I didn't see it or find it, so I don't know details on that one. Today, I was watching the ducklings and they were swimming in their little pool. One of the ducklings got out of the pool and sat down beside it for a minute. Then she got up stumbled a few steps and laid over. I went to check on her and she was dead. She had blood coming out of her mouth. Any ideas as to what would cause this? If it is a sickness, how do I prevent the others from dieing?