I reckon they are being provided with Vitamin D supplements. As far as the mental health aspects of natural light, maybe they're sending down natural spectrum lights in the palomas.

I think they don't want to get the miners' hopes up too much about an earlier than expected rescue. The miners are involved in their own rescue by clearing rubble from the drilling, which has to be quite therapeutic in its own right; they aren't just helplessly waiting.

This has got to be the most amazing rescue attempt ever.