Thank you for your kind words. Here is what I know so far: the vet sent her to Auburn for the necropsy so no word yet, and 3 stool samples from hen #2 turned up no cocci or worms (although I imagine maybe if the worms weren't shedding they may not show up in a stool sample?) Tonight we are removing food from the coop so we can do a crop check tomorrow morning, and anyone with less than an empty crop will get an Epsom salt drench. There are currently 4 chickens I am concerned about that share the following symptoms: feather loss under the vent, feather loss at the back nape of the neck, droopy-ness underneath the vent (as if something is there, like backed up feces or maybe liquid) and tiny black spots on the combs only (nothing as bad as the pictures of pox I've been looking at). They also fluff up their saddle feathers periodically. Hen #2 is the only one acting a bit listless, the others are still behaving normally. I will take some pictures today to post. I've been feeding them as a treat Greek yogurt with crushed up probiotic tablets daily, and I have Tylan for their water which we'll start tomorrow (there's puddles everywhere today, doubt they'll touch their waterer.)
Tomorrow hen #2 (Elizabeth) is going to a different vet I just found that treats chickens (our vet has never worked with chickens before so she was doing what she could).
Seems like salpingitis or egg yolk peritonitis, but as I understand, both of those are a symptom of some underlying issue or are caused by something else. Dry pox is also a possibility, but probably not responsible for the intestinal issues.
I don't think it's ascites because the belly doesn't feel like a water balloon.
Sorry I'm being so wordy, I guess I'm hoping someone will read this and it may sound familiar and can point me in a direction for clearer understanding.
Here's some more info: they free range all day on an acre, 8 layers and 9 pullets (only layers are affected), being fed layer feed with a smaller feeder with grower feed. I've seen both ages of chickens eating from both feeders. They get scratch as a morning snack mixed with oyster shells, I also grow soldier fly larvae as a treat and periodic veggie scraps. We live in north Florida, the 5 month long heat wave caused almost all of the girls to stop laying, we went from 7-9 eggs a day to 1-3. It is just beginning to be in the low 80s but laying hasn't started back up. There have been no eggs since we wormed two days ago. Our local farmer's market chicken farmer has said her hens are the same way, little to no production. About a month ago we experienced what the Mosquito Control guy said was the worst outbreak of mosquitos he's seen in at least 5 years. Our yard backs up to acres of swampy area, and we couldn't go outside for almost 2 weeks without being swarmed by hundreds of mosquitos at once. I had to use a fogger which I wasn't thrilled about but used it at dusk when they were already in the coop and only did the perimeter of the yard (coop is in the middle). The four hens affected are two different ages, either 2 1/2 or 1 1/2. I use the deep litter method, with pine shavings in the coop itself. Not sure if this makes a difference, but the hen who died was the weak one in that group of babies 2 years ago. This is the first time we've had any illness.
Does anyone have a good way to keep mosquitos out of the coop? I'll probably get the pox vaccine as well.
If I am doing something wrong, or not doing something helpful (like maybe ACV in their water?) please let me know. Hoping tomorrow's vet visit will shed some light. My absolute favorite chicken is one of the four, and the thought of losing her is crushing. I appreciate everyone's help so far, it's hard sometimes to even know what to search for and you guys have pointed me in very good directions.