It varied...we had 28 clutches last season, with hatch times between 60-79 days, and they typically pipped 24-48hrs before leaving the eggs. So, if they hatched at day 79, they would have pipped around day 77 or 78. I don't have the detailed records handy, so I can't be more specific. But based on my experiences with lower incubation temps, I would say your eggs probably just need more time.