My rabbit just delivered 4 kits a week ago. She was healthy and feeding her kits. Yesterday I noticed that she wasn't pooping the normal amount of poop compared to my other rabbit that had also delivered a day before her. She also wasn't eating normally because I could see the hay and pellets was untouched. Today while I was cleaning her cage, I noticed that she acted sleepy and kept dozing off. While I was cleaning the other cages, she suddenly started to jump around furiously and started trashing the cage before falling down dead. What could have been the reason?