It's OK we all make mistakes.
Usually with the best intentions. I have myself done similar ... many years ago I had a chicken abandon a nest overnight, the eggs were stone cold, it was frosty morning and they were only a week along. I thought there was no chance and cracked them ALL into a bucket ... then I saw the hearts beating ...
Oh poor babies
... I was 12 ... that made an impression.
More recently I helped a duckling to hatch, who had pipped 3 days before with the others who all hatched, but he hadn't moved, and he wasn't ready after all ... actually I "saved" him with comfrey salve on his yolk sack, he took a week to finish and walk, and he was the friendliest little darling, but he died in the night when he was over a month old! I could have sworn he was alright ... he was perfectly healthy and growing fast. I don't know what went wrong, but I'm sure it must have been because I damaged him.
The remaining eggs will be fine, only an hour chilling is not much ... they live for days sometimes. Yes, they can develop slowly if the temperature is low. You can also get leg issues (splay leg), but I don't think you should with only half a degree low. Still watch the legs as the chicks dry out and walk and be prepared to put some little hobbles on Immediately if they are doing the splits!
If your air cell is too small, I would suggest future incubations should be run at a lower humidity also. You can't really change that now as they need humidity in the last couple of days to help them hatch.
For future reference, we all have to check out eggs that may be dead on a regular basis ... the trick is,
a) if you know chicks have developed, don't worry if non-one hatches until day 23 at least. Later is possible. On the other hand, if everyone but a few have hatched and those haven't moved, maybe it is time to check them.
b) candle, mark the air cell. That water candling method is a good one too. If no signs of life, use a little knife or screwdriver to scrape a small hole in the air cell end. Enlarge this until you can see clearly. You should be able to tell if the chick is breathing. If not, use a clean cotton bud and touch it gently ... if it is stiff and doesn't move, you probably have a dead chick and can proceed.
c) if the chick turns out to be alive, damp the membrane in that air cell with vaseline or distilled water, now take a careful look, if there is what looks like egg white left, and bright blood vessels, leave it alone. If it looks thin and quite dry, you have to make the call as to whether you think the chick is stuck or not. That is always hard to make ... if you help, do it little by little, from his beak, and every time you take some shell away, put him back for a half hour or so.
Even the tiniest wiggle indicates there is still hope. I don't ever attempt an eggtopsy without water candling to be sure there is absolutely no wiggling.
I do get impatient and water candle right after the end of Day 21 if I don't see or hear anything when I candle the eggs at the end of that day. If I get a wiggle, I carefully pat dry the eggs, without rubbing, and return them to the incubator.
Then I wait, even more impatiently than before.
