Your young chicks will need to be 4 months old before being with the other pullets without restrictions. You can put them behind a partitions where they can see without touching, at 3 months. That should make flock easier to integrate at 4 months.or if at 3 months you could arrange your coop to...
Sure, Chicks start out at 95* and go down 5* per week, so yours are at 90*. If your temps are ok outside during the day, it's the dips and inconsistent temp at night and early A.M. that need to be controlled. If your using heat lamps be sure to chain and use a C-clamp, not the clamp that comes...