leaf problem

some of my upper most leaves have began to turn slightly yellow at the tips and have curled towards the 600w light. COULD THIS BE JUST FROM HEAT???
also some of the mid section leaves have blackened tips but other wise the plant is growing strong (roughly 2 inches a day) i knnow i have asked this question before and was told it was too much nutes. but i read somewhere that this could be a potassium deficiency.
any suggestions welcome

sounds like a tad to much nitrogen. but since you insist.......


You need potassium!

do you think? havent fed it anything in about 3 weeks and it has shot up about 2 foot since.

high ph,lacking in iron bro!