Yeah, totally seconding everyone else saying encouraging getting a necropsy done. And if you do, I really would give you a big loving hug and a kiss fir posting the results here as it’s sooooo incredibly helpful when people do this.
When I first read your thread title, I was going to ask you if there was any fireworks in your area the night before. I lost two hens due to sudden fright from a neighbor setting off illegal fireworks right over my coop. Chickens being prey animals have a death reflex when something startles them suddenly ir if they are feeling a certain pain threshold they just die…. …but it’s probably not in your case.
(EDIT: I thought you said blood and not bodily fluid. Keep that in mind reading the following). The blood in the towel ..do you think this is from her vent? My second thought after reading that is it could be coccidosis. I had a mother hen (with peeps) get it. I noticed in the evening a little bit of blood in her stool. I had no Corrid to treat her and planned on going to the store the next morning but by the morning she was dead. Some Cocci is SO quick to kill. If there was blood in her stool, then it’s a big possibility that’s the culprit..if so, you should treat your flock immediately with something like Sulmet or Corrid (Corrid being typically more effective). Look for blood in stool. In my case, my flock was previously infected and the stool looked as though someone poured a small vile of fresh blood over it. It was that evident. They survived though because of treatment.
Poisoning also is a factor, but the blood on the towel doesn’t seem likely, though it could be- depends on the poison I’d think.
There are also genetic factors. (Bad hearts/livers conking out early) Some birds will just reach a point where something genetic and festering gets to its breaking point. Again, the blood on the towel doesn’t really suggest this.
No way any predators got to her at night? Rats? Rattlesnake bite? Mites?
A necropsy at your state ag center should be free. Your vet might do it too. Death causes are often hard to pinpoint unless one has one done. I did a few (or attempted) a couple times but ceased after I realized doing so being untrained could cause me to get sick, so I Don’t suggest it, but it’s a last resort. Even at that, not having the equipment and knowledge of pathogens doesn’t help.
Anyway, I’m sorry to hear about your hen. If it’s any consolation, it sounds like it was quick, and after taking care of sick birds, I’d have to say those that go quick, have it best. Please watch out for the rest of your flock- cocci is my best guess.
