Tips of leaves yellowing?

Growing an auto with cfls in soil and it has begun to show signs of sex, well the other day I noticed one of the leaves was a yellowish brown, but I didn't think anything of it cause it was pretty close to one of the lights so I figured it just got burnt so I moved it back then the next dah there was a another so I set it back even further from the lights, we I wasnt able to check on em for a couple of days and I checked this morning and there's like twice as many. It starts just being a yellowish brown then the very tip ends up dying and shrivles away.
Is this a lack of nutrients or what? Cause all I hav been giving her is water and love lol.

And at the top of the stem there are purple streks, don't kno if theyr related

It sounds like you need cal mag my friend, pics would hepl

I'm workin in gettin a camer I kno I'm sorry thanks for bearing with me. What I was reading I think it could also be a potassium def it sed lack of potsas. Will cause the leaves not to be able to keep a regulated temp so in higher temps the tips burn cause they do look kinda burnt. Is this possible? And what exactly is cal mag lol sorry I'm still new to this and again thanks for bearing with me.

I went ahead n trimmed em off tho

Cal mag = calcium magnesium. There are several products on the market that bundle these two supplements together.

I'm going for All organic bit te more and more i read into it I think it's potas, I'm gonna try adding some wood ash and see if that doesn't help