Zebra finches dying in nest

Question

Serenity #2   I have had zebra finches for a year now. When I first bought them I had a small cage, one of the parakeet kits ones with the lids for the feeding dishes. I bought a male and a female. I didnt put a nest in the cage at first. After a week the birds were sleeping in the covered food dish and the female broke her neck and died. So I removed her and within 2 days bought a new female (which I believe may be male), and a finch nest. Everything has been wonderful. No pecking, eats well, fresh water daily, no dominating behavior or feather picking. They have been wonderful birds. I even upgraded to a larger cage over the spring this year. This morning however, my daughter could not find the original male, named Rio, in the cage. I looked in the food bowl (yes it still freaks me out)...I found him in the finch nest, squished, couldnt see really well but I believe his neck was broke as well. I threw away the nest totally. Now I want to know if its safe to have a nest? Should I get a bigger one? My plan is to go find another bird tomorrow or Friday (today is Tues) will the other one be okay till Friday? I know they can get lonely and stop eating. I am attaching the picture of the one I have left (was told it was female but have feeling its male, they never had any eggs together). My plan was to at least have 2 babies at some point to bring our total to 4. My mom has always had society finches so I have been around finches, but I find the Zebras cuter and their sounds very soothing. Can you give me some recommendations? I don't think I can put my daughter through finding more dead birds.(It was fish before birds...I prefer birds) Thank you kindly!

Answer
First off, how did you come to the conclusion that the birds broke their neck? While it is possible for a finch to break it's neck, two in a row is a little hard to believe.
Assuming it is the nest, what kind of nest are you using? Zebras prefer a covered Wicker nest to any other kind. A nest box can be used when push comes to shove. Considering the second one that died is the one that had been there longer leads me to believe that the killer could be something more common; air sac mites. I always try to rule out air sac mites first because it is the easiest to diagnose and treat.
Hold the finch up to your ear and listen to her breathing. If you hear clicking, it's air sac mites (easily treated by using Scatt which is available on ladygouldian.com). If not, it's not air sac mites.
Unfortunately, since I'm not there, I can't help as much as I like. The best I can suggest is get a wicker nest, proper nesting material (available on the same site), and make sure the finch cage stays at a temperature of approximately 28C to help rule out stress and make things easier if the birds are sick. I also suggest buying your next finch from a breeder and not a pet store. Pet stores rarely care about the health of the finches and will come to you sick. A breeder is more likely to make sure their birds are healthy.
If another bird dies, I strongly suggest taking the body to a vet immediately for an autopsy to make sure that this isn't something more serious like E. Coli