Hello, and Welcome! Our small flock has just gotten to that "teenage. furry/feathery" stage as well. You are absolutely in the right place for getting great information from a great community. Happy to have you here!
I know this feeling. I kept waking mine up to make sure they were okay (well, for at least the first couple of days). Once I realized it was normal, I let them sleep, and they are doing fine.
Well we decided that now was as good of a time as any to just get a new brooder box built for our 7 chicks...We immediately realized we needed to move the food and water a little farther apart...lol
We just lost our first chick that was acting this same way. She had pasty butt, which we got cleaned, but she never did really grow or get active with the others in the flock.