late hatches from the incubator

I have incubated three times. The first time I had half the fertile eggs hatch but on days 22-23. The second time was a total bust. One hatch, one pip and no survivors. This time I know 19 -21 were alive and well on day 18 but now it is day 27 and I only had about ten percent hatch on days 25-26. My humidity was usually 55 - 60 % until day 18 when I increased it to 65% which is where it seems to max out. I believe my incubator is cold. I increased the temperature 1.5 degrees F on day 24 and began to see hatches on day 25. At this time there is a pip in the incubator but I don't have much hope for any live birds today. I am ready to clean the incubator and start again with a warmer temperature. I had calibrated the thermometer with one that I believed to be accurate but that has produced one slightly late hatch and one very late hatch. I think I have the temp right now.
Any suggestions

What was your temp at and is it a still air

It has a fan and an egg turner. I believed the temperature to be 99.5 although it read 98 F This is because I compared it to the brooder thermometer, which I believed to be accurate. When I raised the temperature to read 99.5 I got pips. It is day 27 and there are 9 eggs in the incubator. I did the float test and that was useless. I already knew which ones had an air sac. I opened some of the ones that sunk and killed a live embryo. So I quit. I opened another one 6 hours later and although the baby was dead, there was still fresh blood in the vessel so I quit again. I don't have the stomach to kill embryos. Grown chicken for food yes. Babies No. I don't believe any eggs are going to hatch at this time and I want to clean the incubator and reset it with the warmer temperature but I am afraid I'm going to find live embryos again.

Sorry to hear your havng problems

My thoughts would be with what you have described that the temps are too low causing late hatch. I would get another thermometer just to be sure. I hear the Brinsea spot check is good. Also if your eggs are getting to lockdown and then dying that would point me towards too high humidity during incubation. 55%-60% is too high in my opinion for day 1-18. I find 45% adequate for the weight loss needed and air sac growing large enough. Humidity needs to be an average over the entire incubation period short term changes shouldn't be a problem.
Hope this helps and good luck in the future

https://www.backyardchickens.com/a/hatching-eggs-101

This is a great read very usefull with lots of extra links on various topics

My first attempt at hatching was a bust. Day 24&25 I had two (out of 17) hatch, the second died. My thermometer was off (reading higher than actual) by 6 degrees. I am at the end of my second hatch now. I used 3 thermometers this time to make sure it was within 1 degree of recommended temp. I also did a dry incubation monitoring the air cells throught out the first 17 days until lock down on day 18 when I upped the humidity. (I also used sponges to maintain humidity this time.) I have 10 healthy fluffy chicks in the brooder and another 3 that have pipped. I don't think the last 3 are going to do anything though I have time as it's day 21 for me, but if the last three are good that'll give me 13 out of the 16 that went to lockdown. I am using a little giant incubator with fan kit and turner and my eggs are local, from my sister's hens.

I'd tap into the eggs at the air cell to check for movement and life before tossing or cracking if you are still worried about there being live ones.

Sorry to hear you are having such bad hatches.

Do you think the relative humidity locally affects our incubation humidity requirements?

Depending on what type of incubator you have, yes the relative humidity in your area can have an affect on your incubation humidity. As @AmyLynn2374 said maybe you could try the dry hatch method if you have high humidity in your area. I've never tried it myself but have read quite a lot of success stories with the method. There is an article on it in the learning centre in the hatching and raising chicks section.
https://www.backyardchickens.com/a/

Day 23 on my hatch and nothing. Yesterday they were moving. What should I do?

If they were moving yesterday I wouldn't panic yet, it may just be a late hatch. I don't give up on them till day 25. There isn't much else you can do except wait and see.
Hope you have some action soon