I am down to only 3 silkies in the hatcher. 2 of these the air cells are on the small end of the egg so I'm not holding my breath on these. The other silkie finally pipped overnight on Day 22 and doesn't appear to be doing anything now. I really don't want to lose this one and will intervene when necessary. How long before it should start to zip? Also, will it start to zip at the pip hole?