I have a 3 yr old black Astralorp who was broody at the first part of July. We were able to break her of that in about six days. Today when I let her and her 5 other flock mates out to free range and there daily treat I noticed she fell backwards. I did not think any thing of it, but she kept doing the same behavior several times. Almost like she was having a seizure, her head went back and then she lost her balance and would fall. I noticed she is loosing feathers, but being she was broody can be normal. I have six chickens total ages 4,3 and 1. They have a large wooden coop and a large fenced in area they roam until around 2:30 then they have free range of the whole yard. To be honest I was not as attentive today as I normally am. I did see the chicken in question first thing this AM and did check on them from the window several times during the day and let them out at 3pm for there treat and social time (free free range time). In the area they have to roam protected from predators there are 3 watering stations one with ACV and the other with fresh water. 4 feeding stations one with a scratch and peck feed the others are nice quality Layer feed. 3 areas of oyster shell and grit. Several areas for shade and to lay eggs. I did a search and gave her or tried to give her 1000 mg of vit E and gave her 600mg of calcium. She is in the garage with food and electrolytes. I don't see any injuries. She is vaccinated for Marek's disease and everyone else is doing well. Any ideas?