My mother started incubating her duck eggs seven days ago. They're being hand turned 3-4 times a day, and she got them straight from a breeder, no shipping or rough handling besides brushing off the clumped mud and crap. Tonight while candling them she noticed multiple egg yolks were moving from the center of the egg and were kinda sticking to the sidewalls. I have never seen this happen before and I'm wondering if she should even keep incubating them? Has anyone seen this before? What could cause it?