Please see this picture of my banana tree. It is a dwarf Cavendish and it was growing pretty well indoors in the pot I got it in. I decided to re-pot it into a nicer looking pot but the new pot was "self-watering" and I think the soil got too damp. What I did was drain the soil and put the plant outside in the sun. Now, as you can see, two of the leaves have gone this drab colour. What has gone wrong? How can I fix this? Is it sunburn from a long time getting used to being inside?