I have been told many times by old-timey chicken people and not so old-timey chicken people lol that chickens are prone to heart attacks and strokes. I know for a fact that I lost 4 of my original flock to those two things, according to the necropsy.
They didnt all at the same time mind you!
But yes, it is possible. I think one or two of ours were brought on by stress tho....we had a terrible raccoon attack on our BR head hen Boo..and all 7 of the birds were rather traumatized. (She was so brave defending her sisters!!)
We lost those two thru heart/stroke issues (according to the necropsy) over the next two weeks after Boo died. Finally caught that dang racoon prowling around and needless to say he got the fear of my hubby put into him and we have not seen a coon for over 2 years. We did have one a few weeks ago tho, but the girls seemed to be ok and didnt panic as much this time. Course they called out the alarm and my hubby came rushing out to the rescue of his girls lol It was actually quite cute to see them run to him when they saw him come in the pen lol