I guess this is not unusual? Out of 12+ silkie eggs (I think there were 14 maybe?), 4 were clear at 1 week. Ok, no problem. Candled again around day 18 when moving them to the hatcher, 2 more appeared to have stopped developing. Day 21, 4 pipped, 3 hatched and one of those died immediately (was real small and had a lot of yolk sac material). One still has a red thing at his navel, but is eating drinking and pooping and seems as active as the others. The last chick is completely normal. I also set some eggs from my own chickens along side. Only one was clear, everyone else hatched healthy, no problems. So I don't think it's the bator.