sleepy hen

Please excuse my ignorance, but i'm new to keeping chickens and have only had 3 POL's for a week. Everything seemed fine for the first 6 days, ( 9 eggs between days 3 and 5) nice perky, lively girls. Let them free range yesterday for the first time and kept them out for a couple of hours. They went back home with no fuss. Let them out this morning and gradually 2 out of the 3 has become more and more lathargic to the point that they just sleeping, one of them has got her head under her wing and hasn't moved. Is this normal behaviour or should I be concerned. I've had 1 egg of one of them this morning.
Any advice would be most welcome.  Thanks

Could it be some kind of infection? Hens rarely eat anything that's bad for them. Is their breathing clear? Is there any discharge from eyes or nose?

My buff orpinton sleeps with her head under her wing, but i wouldnt say its 'normal' to do this for a chicken, As you havent had them long, you wouldnt really know if this is normal behaviour for her so you will have to check for other signs of illness. Lift her wing up and feel her temperature, check the others aswel so you have something to compare with as hens temperatures run much higher than ours and they can feel hotter than you would expect them too. Is she eating? feel her crop at the end of the day to make sure there is food there. Does her chest sound clear, are her eyes and nose clear? Sometimes the stress of a new home can cause them to be under the weather a bit. Just keep a close eye on her and if she gets worse, pop her along to the vets.

dont fret too much yet maybe all the changes have upset them and there tired, give them  time and wait and see, hopefully they will be fine