I have a couple of Jacksons , they have an outside big cage with ficus tree inside. I Know how important the sun is for them since I moved their cage to a place that gets more hours of sun. Before they use to get 2 hours of sun a day and I notice that they had black spots on their skin and they were tryng to get out of the cage to stay in the sun. Now they lay in the sun for about 6 hours all the black bumps came out when they changed skin and also they are much stronger , they got a beautiful skin , they don't try to get out the cage and they are much happier.
If you could put your cage close to a window where the sun hits , you will see the difference.Also I think the sun light can prevent skin deseases and other diseases too.