Most chicks I've raised like to sleep in a big "pig pile" for quite some time, maybe 10 weeks or so, until they decide that roosting is better. And yes, they will all suddenly drop off for naps anytime of the day, leading you to think "nerve gas?" until you realize they're just taking a communal siesta.
But the jumping over their brooder-mates to get right under the light makes me also think they may be too cool. Our temps even in Fla have been below normal. Monitor it with a thermometer to be sure.
I wish I lived closer, I'd love to take those lil' SL roos off your hands, they grow out nice & big & meaty. You might be able to find another BYC member in your area, or post a notice at your feed store, and find someone who can take/buy them before you get too attatched.