Well, it held to 78 this morning in the outer edge of the light. Not sure the ambient temp yet, but would guess around 10 or 15F. They seem happy and are behaving like @TheAlrightyGina said would be good. We have been fighting pasty butt and the feathering has been slow like @abpatchy said. I’m so glad I joined this forum!
Higher temps can lead to pasty butt, so yet another reason to keep temperatures lower. From your photo they looks nicely spread around the brooder, so they do seem pretty comfortable.