One of our flock of 10 RI Red crosses was in the nesting box tonight, so my husband pulled her out and she started "throwing up" a clear watery fluid. She was very lethargic and weak, but otherwise looked healthy. Suddenly, she started to struggle a bit, so my husband set her on the ground and then she had a seizure and died. Any ideas of what might have been wrong? The rest of the flock looks fine, but so did she up until this evening.