African Violet with Yellow Leaves?

I have a beautiful, HUGE african violet that seemed to love it's spot near my window. But it's leaves are fading. They aren't drooping, but fading to a yellow color. This is mainly the outer or older leaves, but even the newer ones aren't as dark green as they used to be. What do I need to give it, or since it's so large does it need to be split/repotted?