Interesting! Why would the eggs be harder to incubate? From what I understand Calls are harder cos they got the wee little bills - is there a reason for the silkies hatching difficult? --I'm not being a smartaleck, I'm new and don't know stuff!
The exact reason is not known. The eggs seem to develop well but then things go wrong at hatch. Some think it's a humidity issue, but as far as I know this has not bee substantiated. Natural incubation tends to get much better results.