All eggs but 1 died on day 23. PLEASE HELP!!!

Hello all. I had 12 eggs, great incubator with fan & turner. I have read everything I could find before attempting this. Temps were at 98.5 -99.5 for 18 days. Humidity at 40-45 whole time. Candling looked great. Day 18 moved 10 good eggs to lock down in separate incubator that was run at 99 degrees for a week prior. All water areas full & 3 wet sponges added only brought humidity up to 60. Day 22 first external pip & zipping started an hour later. 24 hours later, chicky died. Dry membrane- paper white. Next chick had started a zip & 6 hours later, I assisted. Only surviving chick! Autopsies showed all dry and white dried out membranes!!! No shrink wrapping. Very late deaths. We're devastated. How can I keep this from happening again? I have more eggs to go to lockdown on April 6!!!! I need help!!! Also lone survivor is sticky & wont fluff out. She's cheeping & stumbling around. I don't want to chill her, but dont want bacteria either! She's our miracle chick. What should I do? We are so worried!

take a warm wet washcloth and wipe her down and put her in the brooder under a light with a feather duster in with her.

It sounds like your temperatures are too low. They should begin hatching on day 21. Increase your temps on your next hatch, and I would suggest investing in a Brinsea Spot Check thermometer, as they are super accurate.

Is your incubator wafer or solid-state?
I have a wafer incubator and it reacts to barometric pressures too much. I now use banty hens exclusively to hatch.
If its a wafer incubator, check barometric pressures last 3 weeks, maybe you had a spike.
Also, what is the fertility/hatch rate of eggs?
Hope this helps.

I run my humidity around that 65-70% range during lock down and my temp around 99-100 degrees during the whole process from start to finish. However, that's for a circulated air incubator. If you have a still air I believe the temp is supposed to be around that 101-103 degree range and humidity probably the same. Hope that helps. I too had issues with the dry membranes but was able to get the humidity up before I lost any more of the chicks during hatching.