My prayer plant, Frank, has been doing well all season. I repotted him into a bigger pot in early spring because he was root bound and he has been growing like crazy all season. He even has a couple of tiny white flowers. However, today I noticed that one of his leaves is totally yellow, while the rest are still quite dark.

He is in front of a window and with the weather change I think he's getting too much sun and needs to move (some tips are browning) but what is causing the yellow leaves?? Is it the sun? Do I just need to move him? Poor Frank.