Once a White Knight reverts to green, it is hard to get the variegation back. You can try a couple of things to get the variegation back. We suggest pruning away any green leaves that appear to encourage the variegated growth. Or cut the stem till the point the plant has variegated leaves and petioles and continue doing it until you get variegated new growth. You can increase the light intensity from 250 CF to 350 CF or keep the plant in bright light for twelve hours daily.