They'll be fine. I live in Northwestern Wyoming. We've already had snow...5 inches on October 12 and more earlier this week. As long as you let them acclimate to the ambient temperatures naturally, they do great, and you seem to be doing that. Here sub zero temperatures are not at all unusual and the first year I had chickens I put them out on April 1st. Two days later it snowed, and we got our last snowfall of the year on June 6th. My chicks were 5.5 weeks old when I put them out to live in the coop.
I don't heat or insulate my coop/run, and I don't even use heat lamp for chicks out there...just a heating pad cave in a pen within the run. They thrive, even though our springtime temperatures are in the teens and twenties at times. So as long as you have good ventilation (and lots of it) keep them dry,and have no chilly winds ruffling their feathers around and allowing trapped body heat to escape, they will handle your Florida temperatures with no issues. Humidity buildup from droppings, their respiration and the waterer (if it's in the coop) are the enemies, not the actual temperatures. Oh,and yes, I have Silkies, Easter Eggers, and several other kinds out there.