This year I added a gigantic fan called Port A Cool it has a water tank and lowers the temperature significantly in their shaded area. Like @father0fnine ive lost a bird almost every summer. They usually have something else going on internally and the heat zaps them sooner than if there wasn’t heat.
They have been at 37.5 Celsius (99.5 Fahrenheit) for the whole time. I put them next to the side of my incubator so I can candle them from outside but I haven't seen a broken air membrane in the blue one and I can't see through the other one because it is a darker speckled brown. I hope they will be OK. The speckled one responds to my cheeping with movement so I'm sure it's still alive.
Your eggs are probably right on time. If temps are just a little low, they can be a couple days late. If the eggs are responding to sound, then all is well. They should start pipping soon. Often you can't see the tiny pips. It may only be a tiny hairline scratch on the surface that can only be seen when light shines from just the right angle..... or the pip could be positioned away from your viewing window and impossible to see. If you "hear" your eggs peeping, then you know they're pipped &/or zipping.
