Hi...I'm new and this is my first hatch. All my eggs have really nice size air sacs like what I have seen in diagrams for the size they should be at this point...except one. The air sac is maybe a hair bigger around than a nickel. Will it be okay? What would cause one egg out of 5 to be different? It is a standard size light tan colored egg. The chick inside is hard to see as all is dark but I can still see movement in what tiny bit of space exists below the air cell...so I know it's alive. Any ideas?