yellow tip on 1 leaf

[Chicken]

the tittle explains it all.

1 of my plant has a yellow tip on one of its leaf. Whats kinda ackward about it is that it's curled upward. I'm using FFOF and 150watt CFL. I'm not sure whats wrong with it. can someone help me please??

also i'm using a alarm clock which has a temperture display and it say the temp is around 83 degree ish. I know i need to go out and by a more dependable one. will it be okay at 83? because i know that it should be around 65-80.

[bigbudz]

I'm still new to the whole growing thing, but i'm pretty sure they're all gonna ask you what your PH level is. That seems to be the culprit 9/10 times when the leaves are yellowing.

[Chicken]

awwww that i dont know, i don't have one of those meters. I'm using distilled water to feed.