I put 12 eggs in my home made incubator at 4:00 pm on February 18. I expected hatch sometime tomorrow, March 11. This morning I woke to 1 chick and 3 external pips. Chick number two zipped and hatched a few hours ago. Pips 3 and 4 have not made noticeable progress in the last 10 (possibly up to 18) hours. Should I consider assisting or just let what happens happen?