Bummer... I had to consecutive hatches of ZERO, before this hatch, so I feel for you!
My incubating history is long and has a few chicks sprinkled in there with all the eggs I've had to toss:
1. 12 cooked eggs (lesson: don't use a crock pot, it's for cooking, duh)
2. 1 lone survivor (lesson: check your thermometer against a thermometer you know is accurate at the temps you're using, not just accurate at room temp, duh again) (Ironically, I lost that chick to heat this summer, she hatched in April, she's the one on my wallpaper.)
3. 12 eggs, 0 chicks (lesson: separate the eggs from the heat source, duh some more)
4. 3 eggs, 3 chicks (lesson: hatch in small batches, forget hatching a dozen eggs at a time to get half a dozen chicks; somehow chickens and eggs just don't understand math, duh should go without saying by now, but I'm going to keep putting it b/c I feel like an idiot and I hope that others can learn from my mistakes/stupidity) (also, I subsequently lost these and I don't know why; this spring was a bad time to be a chick is the only explanation I can come up with.)
5. current hatch 5 eggs to start and 4 eggs left (lesson: don't turn/candle w/ a zillion children around; that's literally impossible at my house, but hopefully others can avoid this)
I think I probably missed one in there, but the results were the same: no chicks.
-Keep temp consistent (within 2 degrees or less of where you're aiming)
-Turn an odd number of times a day so the eggs aren't on the same side for two extended periods of time in a row.
-Rotate, every incubator (no matter how good) has cool spots and hot spots.
-Hands off during lockdown; there's a reason they call it "lock down"!!!
If I build an incubator, I'll install a thermostat and a fan. I like turning, so I won't put in a turner. I also want to put a plexiglass viewing window in the top; I like being able to watch them hatch and I want to be able to check the temp during lockdown w/o having to open the 'bator, but mostly b/c I like watching them hatch.
Sorry that's so long...
I'll copy and paste this on my own thread, then I won't forget where I have and haven't posted it.