Looks to me like you heat stressed it off the lights. Was that leaf close to any of your lights ?

Other than that:
I would say it is a phosphorous issue. Phosphorous is vital for a plant especially during the bloom stage. It is the most important for blooming.
silent leprechaun Reviewed by silent leprechaun on . Help.....please Im a noob when it comes to this, whats the most likely cause of this happening to the leaves. I dont know if they are indicas or stativas, i just know the name it was given "purple princess". It was from seed. They are aprox. 2 months old, growing indoors with a sunleaves pioneer VI 6 x 54w relamp with T5 HO 54w fluorescent type lamp 120v 3A 60Hz 324w. The bulbs are vitalume plus Grow bulbs. They are in 5 gallon buckets using Scott's moisture contol soil. I used root and grow for their first Rating: 5