Heather, forgive me if I have the wrong idea, but I think you are a brand-new chickie momma with no prior experience. You will continue to wonder how chickens do the things they do when you aren't looking, and be amazed and astounded by the stupid and/or adorable things they do when you ARE looking.
So, based upon my guess, let me offer some warnings, for newbie chick owners:
When you look in the brooder and they are all dead, do not have a heart attack yet. Tap the side of the brooder first - the chicks will wake up. They just fall asleep like that. Sometimes on their backs, or with their heads across stuff in the brooder (like laying their heads on the chopping block). They DO look dead, but they're just asleep.
When you pick up a chick and feel a tumor on its neck, do not panic then, either. That's a full crop. The chicks are piggies and will stuff themselves. That crop will empty over night and be all normal again in the morning. Not tumors. Whew!
When you see one or another chick on its side, kicking and twitching, it is NOT having a seizure. It may even flap its wings and roll over onto its other side to do it some more. This is dust bathing behavior in the brooder bedding. Perfectly normal. And very silly looking once you know what it is, which is NOT a seizure. Trust me.
And a bonus, fourth warning: You will fall in love with them. This will not change even when they grow up into chickens and start to lay eggs. You will love them more. And I bet you will do a great big dance and run excitedly into the house, screaming with delight when the first one lays her first egg.