I washed all eggs with antibacterial soap and let them set a few days before putting them in the incubator. At around the 7th day these dark grey rings appeared on just the Khacki Campbell eggs and not the Pekin eggs. They have live bouncing ducks inside. Just concerned they could burst. But are very uniform and it's just around the very top of the eggs. Is this normal for Khacki eggs or could it be a bacterial infection. I can post a photo. Thanks!