Candling on day 17

Ok I'm really new to hatching eggs in the incubator. I have 14 silkie eggs and the rest are a mix of hens ( Rhode Island Reds, leg horns and Red Rock Cross) breed with a Bantam and Ameraucanas roo. They are due to hatch on the 26th so three more days. I turn the turner off tomorrow (Right!!!) Then just leave them in the bator on the floor rack and no more turning???? Is this what everyone calls lock down???? So I thought I would give them one last look to see how things were going ( and because I'v never seen anything like this) and I candled 2 of them. Really I have no idea what I was suppose to see. What I did see was a big black shadow covering most of the bottom of the egg. Did I see what I was meant to see or did I pick two duds to look at?? I guess I can just wait and see what happens Monday. I really want to get this right because I would like to do a batch of Marans eggs next and a few mix chicks for my cousin. Anyone help me out??