Candled my duck eggs on day 7 and all but two have obvious development and veining!! However, several of them only have veining on one side of the egg--so say on the "front" of the egg, they have beautiful development, a clear embryo, dark, compressed looking yolk, etc. . .but as I turn to the back there is. . .nothing. Just complete blank. . .until as I turn it starts again on the front side. Is this at all normal? Or is something wrong here? I have my eggs in cartons (with the bottoms completely cut out) because so many had loose air cells. . .now I am worried if somehow the cartons could be cutting off the air supply, thus altering the development on one side? Or maybe this is just completely normal and I didn't notice it with my last egg?? Thanks for any help!