Stress. I had a duckling that would almost faint every time it was scared. Reminded me a little of a fainting goat, but more concerning like it was sick or something. Once I realized what was going on, I was able to care for it so it didn't get as scared (because I'm certain it had to do with lack of oxygen, it had a deformed beak with one slit of a nare).
Since there's no video to look at yet, I'd guess it's either playing opossum or decoy.
Unless... if all your ducks are doing it and you don't know what the trigger is - you definitely have to get us a video and detail as much information as you can think of /timeline that you can remember. There are some nasty diseases and poisons/toxins that attack the central nervous system that can cause those types of symptoms. The first thing I would look to is hardware disease or pesticide/herbicide poisoning.
To do a video, either login to YouTube with your gmail account or create a new youtube account, then upload the video making sure it's public, and paste the link back here. Alternatively, if you're a member of the Facebook BYC group, you could post it there and get help.
I’m not that technically inclined. Just picture
