I don;t know. I was wondering if, given the protien content, they may have bloated. That would explain them going down, rapid breathing and stiffness. But the fever??
I guess if I were shooting from the hip I would try to treat the symptoms until I could get a vet or neighbor to help. You could (I would) give a shot of banamine, this is an anti inflammatory ~ it could help with the rapid breathing, stiffness (I am assuming here that those symptoms are a result of pain), and fever. What exactly is their temp?? It can elevate some due to pain, or more do to an infection. If it were a potential infection I would suggest antibiotics. If it is not an infection, I would advise against antibiotics as they could cause worse stomach problems/diarrhea. I would strongly suggest getting a probiotic paste into them ~ it will probably help and it can't hurt. Can you get them to drink anything?