I think that one of them was the culprit. They were eating chick starter food with electrolytes/vitamin pack added to their water. Just today I switched them to gamebird feed. It was three out of 9 that had it and two of them are also just getting over eye injuries I think. I noticed one of them pecking at one of the neck injuries today a few times I stopped him and he went right back to doing it. So I think he was the culprit of it all. I have him in a separate brooder with a friend right now that is one of the larger ducklings. I will monitor that one and make sure he doesn't get injured too. There wasn't room to put him in just a separate area as they are in our classroom brooder. They are going to their new farm homes tomorrow or Friday so I am hoping the three injured will get a good start on healing before I send them home. I have been doing triple antibiotic ointment so hopefully that helps.