Lost my favorite hen to a Prloapsed vent. Looking for advice to prevent this in the future.

This is Mrs. T.. my last Wyandotte. Last week she proloapsed her vent. I spent much time that day on BYC and found alot of great advice for treating it. I cared for her for 5 days and was finally going to take her to my local vent for a purse stitch because the proloapse was not gettting better. Thursday morning, I found her dead in her dog crate I was using to keep her from being picked on by her coop mates. I was devastated! I thought she was getting better. Vet says she probably tried to pass another egg and died from peritonitis. Does anyone have advice about preventing this in the rest of the gang? I have White Plymouth Rocks and RIR's left.

 

I hope for both our sakes. The vet suggested it was from being overfeed and too much light in the winter. Stimulating them to lay more than they should. This is a bit confusing because they have thier feed, some scratch grains in the morning and every once in a while a table scrap. I had the light in the coop on for 13hrs a day. I have turned it down to 10 hours based on her advice.