Hi there!!

They don't all hatch on the same day. Most birds will usually lay 4 to 6 eggs. And most of them will lay every other day. Most birds start to sit on the eggs after the second one is laid. Usually Quaker eggs hatch around 19 to 21 days after the hen starts to sit on them. So you may have one or two that hatch on the same day (I've had that happen with my Cockatiels), but for the most part they'll hatch every other day.
As far as the shell goes...I would just leave it be for now. You have to be
very careful when removing shells from a newly hatched chick. When they hatch, the baby draws the egg sac into it's abdomen, without this, they can die. If the baby is still drawing that egg sac into it's abdomen, you don't want to remove the shell. Usually, a baby should completely hatch within 24 hours.
Also, you might want to be careful about checking the nestbox so much. A lot of Quakers don't take kindly to being bothered and they may abandon the babies.