have one leaf.....

i have one leaf that is at the top of the plant that has a red shimmer in the middle anyone have any ideas will put up pictures in a little bit

T5 (4ft 8 bulb 3000k)
6X 68w cfls 2700k

growing in coco perlite mix
using 3 part ph tech. grow bloom micro nutes
temps are 68-72 deg lights on and off
RH is around 25-35%
3 weeks into flower
5 gal felt pots
Lst'ed

problem started before a watering, after watering and three days later it shriveled up and started to die, only leaf to do this the rest look amazing
it started about a week ago the rest look really healthy

thanks ya'll

what it looks like now.....

looks like water/light burn. Did you get that leaf wet?

no i contemplated light burn bc i had another leaf that got bleached in a spot bc i was gone for a vaca for 4days and came back and it had grown out to the light but this was well before they grew as much