Ok so I had 5, 3 week old ducklings. 2 went missing so we panicked thinking a predator got them. We moved the remaining 3 into the barn. Within days, I found one, #3, that I thought was dead. When I went to remove it, it was barely breathing. I tried to help it but it passed later that day. The next day, again, I found yet another one, #4, that was showing the same symptoms as #3. I quarantined him and decided I had better take the last one, #5, as well, even though he seemed to be ok. Well the sick one started to seem better as the day went on, but sadly it passed the next day. Well I still have the last one, #5, and he seems to be doing fine. I've had him separated for about a week just to make sure. How do I reintroduce him to his mom?