Good morning, welcome to BYC.
I'm going to say, for the sake of the chickens, that you need to do some research before you get more. 8 week old chicks probably need to be contained in a run, rather than being allowed to roam. Best of luck.
Good morning, and welcome to BYC. I'd be concerned that a predator took your birds. I provided a local source for started pullets on your other thread.