Egg issues

My hen laid 4 eggs, one had a collapsed air cell and one was cracked into the membrane on the 4th day. She has two left, both are doing well and staying warm, however I cannot see a visible embryo when i candle them. They are still red and i can see some movement, but i cannot see the shape of an embryo at all. A few days ago, the shape was present and you could see the hearts beating. Is it possible they have died? This is my first time letting my tiels breed and i dont know if i should worry or if i am being overbearing.