I don't hatch duck eggs, just chicken and on rare occasions turkeys. But the same should hold true for all poultry eggs.
There are several different things that can influence when an egg actually hatches. Some include heredity, humidity, how and how long the eggs were stored before incubation begins, and just basic differences in the eggs. A big one is average incubation temperature. If the average incubating temperature is a bit warm the egg can pip and hatch early, maybe two days early. If it is a bit cool they can be late. I regularly get eggs that hatch two full days early, both under a broody hen and in my incubator. Others say they regularly get late hatches, even under a broody hen.
Some eggs hatch earlier than others. I've had hatches that were totally over in less than 24 hours after the first one pipped. I've had hatches stretch over 48 hours, well into the third day after the first one hatched before the last one hatches. Each hatch is different.
I personally do not think you should be that worried. I know, easier said than done. But you are still well within the window of when they could hatch and be fine.
I'll also ask if you are counting the days correctly. It's a real common mistake. People want to say "one" when they put the eggs in the incubator but an egg does not have 24 hours worth of development until the next day. An easy way to check your counting is that Day 28 should be the same day of the week that you started incubation. If you started them on a Monday, the 28 days is up on a Monday.
If you entered lockdown a day early do not worry. That's not a big deal, people do it all the time and still get great hatches. By that time the egg does not need to be turned anymore and it has probably lost all the moisture it needs to so it can hatch. It's something we should try to get right but your window of opportunity is wide open.
Good luck on the hatch. There is nothing you can do at this point that will make a difference so patience is your friend. Don't do anything dramatic, much as you may be tempted.