My silkie chicks are now 6 weeks old, and have been living in their coop/run. It is mostly shaded, but does get some sun. I decided today that maybe they need some more sun, so I put them in the grassy area of the yard and they stretched out and seemed to be enjoying it. Did this for about no mor that 5 min, and then started panting heavy,and then headed for me in the shade. Are they just not used to that kind of heat? Or what is it?