It is possible to over light your plants.... it can also happen in nature at very high elevations... the plants will turn white/yellow... they loose their chlorophyl... it is different than necrosis, the plant will look healthy except the top will be white/yellow... the growth in this area (usualy just the top of the plant in indoor situations) will stop and will not continue until the light is reduced... when the light is raised/reduced the top will turn green again and growth will resume..

: )