If they move around the whole brooder area when they’re awake I’d say the temp is fine.
They probably just like sleeping close for company.
When they’re cold they just stand around bunched up and don’t explore much.
They look miserable when they are cold, with a sad little peep noise. Not a happy little chirp. You'll soon learn the difference.
Don't be surprised when you see them just plop over in their tracks -- they fall asleep on their feet, and tip right onto their faces. The first time mine did that I was concerned, but it was just a "tired baby".
The first "dust bath" will also look really weird. My chicks did it on day one, in their food bowl, and I thought they were having seizures!
They are funny little creatures.