I have them myself at the end of 3 weeks no head plate indoors and they pant starting to think they make themselves warm when they plop down in one spot and is completely unavoidable. I figure if there that hot they'll stayed up and get some air flow around there bodies.I would make sure you have a shaded spot in the brooder. I have larger ducks and as ducklings they spent most of their time outside of the heat lamps rarange.
Hens go broody when you don’t want them to… and won’t go broody when you do. 