I check to see if there is peeping, but I put my ear to the incubator rather than open it up. I do lockdown, and the one time I did open the bator to remove the first chicks that hatched ( it worried me that they were knocking around the few unhatched eggs), the one remaining that finally hatched ended up with splay leg. Now, I have heard several reasons for this , only one of them is opening the incubator and losing humidity, but I tell you I wish I hadn't.
If I hadn't, I'd be sure that it wasn't my fault.
I assume there is a reason that sooo many people before me believe that it helps to "lockdown" the incubator that I'm not going to risk it ever again. After all, does holding an egg up to your ear make it hatch faster? I'd just leave them in there for another day or two regardless of hearing peeping or not.
Do you have a way of pouring water in there without removing the top? perhaps the next batch you should modify your 'bator so that you can. And I hope your babies are just late bloomers! Good luck on your hatch!