Hello guys. we have 4 Pekins that we hatched from an incubator that are now almost 4 months old. (1 male, 3 females.) We haven't had any problems but this morning I noticed one of the girls acting very strange. She wasn't staying with the others and seemed "off." I checked her out and didn't see any injury. I added a little apple cider vinegar to one of the buckets of water when we left for a football game, just in case she just got overheated. (It has been very warm here this week.) We returned to find her deceased and the others seemed to not understand why she wasn't coming in to the night box with them. My question is: how on earth am I to know what happened to her? Do I need to do anything to ensure my other ducks don't die as well? Any help would be appreciated. They have all been doing so well and our lives have been so enriched by these ducks that I'm kind of in shock at how fast this happened.