but I figured it won't change the outcome,
		
		
	 
You are right, candling will not change the outcome.  It can help you make decisions.
There are several different things that can affect when an egg actually hatches.  Temperature is the one people fixate on, it is important and is often the cause.  But heredity, humidity, how and how long they were stored, or just basic differences between individual eggs all play a part. 
When I incubate eggs either in my Hovabator forced air incubator or under a broody hen they are often one or even two full days early.  Yes, I calibrated the incubator temperature, the factory settings were wrong.  This happens after it was calibrated.  It happens with broody hens.  It is not just temperature.  In this case I think a good part of it is heredity.   In my first hatch with it some were pipping as I went into lockdown.  Those still hatched fine but it was temperature related.
Many of my hatches are over within 24 hours of the first one hatching, whether in the incubator or with a broody.  But not all.  I've had some stretch out more than 48 hours.  Each hatch is different.  I remember one hatch where one chick hatched one evening.  24 hours later I finally saw a pip.  I admit I was starting to worry.  The next morning 16 more chicks had hatched out.  That hatch was then over.  That one stretched out about 36 hours.  I've had worse but at least they were steady.  
A chick absorbs the yolk before it hatches.  It can usually live off of that yolk for over 72 hours.  It doesn't hurt for them to eat of drink before that but that's why they can be mailed, they don't have to eat or drink immediately.  This enables the first chicks that hatch under a broody to wait on the later hatching ones because the hatch can be spread out quite a bit.  I once had a broody hen that hatched her first chick fairly late on a Monday.  She did not bring her chicks off the nest to get them food or water until Friday morning.  That was probably 84 hours from when the first one hatched until it ate and drank.  They were all fine though again I was starting to wonder.  I have no idea when the last chick hatched under her, I leave my broody hens alone when they are hatching.  I'm using hours instead of days because it is easy to get confused when you use days.
Your eggs are shipped eggs.  Shipped eggs can be problematic.  You don't know how old they are or how they were handled during shipping.  I once had a 20% hatch rate with shipped eggs.  I had a 100% hatch rate once.  You often read that you get a 50% hatch rate with shipped eggs.  If you average mine out that's pretty close but neither of those hatches were even close to 50%.  You just don't know with shipped eggs. 
One time I picked up 30 eggs from a breeder and drove the eggs home over some very rough country roads.  Only 10 of those eggs hatched.  That was my fault.  I did not protect them from getting banged around by those rough roads.  You don't know how rough shipped eggs may have bee handled or what temperatures they may have gone through.
It is possible for incubators to have warm or cool spots.  Mine doesn't seem to.  I number my eggs as I collect them and store them for incubation.  The first egg laid is number 1, the latest is whatever number is last.  I've set the eggs in my turner in that order and kept track of which numbers hatch when.  It's been random.  There is no grouping of the hatch based on where they were in the incubator or when hey were laid.  But that only applies to my incubator, it does not apply to yours.
You can candle the remaining eggs if you wish.  The risk is that you can shrink-wrap an egg by reducing the humidity in the incubator when you do that.  If the egg has not external pipped it is highly unlikely you will shrink-wrap it by opening the incubator.  Your humidity was reasonably high during incubation and is OK during hatch.  That should help prevent shrink-wrap too.  But if you do candle them, try to keep them as humid as reasonable while you do that.  The longer they are in dry air the greater your chances for problems.  You might mist the eggs with warm (not hot) water to keep them moist.  Typically I don't open the incubator during hatch but if I have a reason I will.  There is a risk involved but when faced with a clear emergency that risk may be worth taking.  I did have a shrink-wrapped chick once when I opened the incubator, I do believe it is possible since it happened to me.  Still if I have a reason I will take that chance.
I would like to know if I've done something wrong. Is this common? 
In my opinion you have done nothing wrong.  It sounds like you are about 24 to 30 hours after your first one to hatch.  From what I've experienced in an incubator and with a broody hen it is common.