Leaf dying

Ok, long time smoker, first time grower here. This is all i've done: i bought an already growing plant medically (i have a license) and i threw it in a pot, watered it, and put some lights on it. i have three lamps pointed at it (it's just one plant), two lamps with 60 watt plant light bulbs and one lamp with a bigger wattage one...i think maybe 120 or something. i have the plant on a 12/12 cycle and it seems to be growing fine, but on of my leaves is sying. one arm of it appears to have died altogether:it is brown and dry, and now more of the arms on the same leaf are dying. it doesn't seem to be affecting the other leaves or the plant, but i need to know if maybe i'm doing something wrong? or maybe my setup is bad? someone give me some easy help that can be applied to just one plant.

can you show pictures
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lots of things here.... you need to ph your soil and water... it IS needed. plant maybe recovering from shock of the transplant. 12/12 cycle is a flowering cycle, the plant will grow a lot (may double or tripple in size). you will want to have approx 15,000 lumens on your plant. the more the better.
also, you will want to catch up on some reading... here are some good links

https://www.rollitup.org/newbie-central/1326-101-already-asked-questions.html
https://www.rollitup.org/newbie-central/3423-vocabulary-growing-terms-slang.html
https://www.rollitup.org/newbie-central/1443-free-grow-videos.html

also, check out the grow journal section.

Ok, so pH should be between...? i just put her lights on and left them on all night, so she's been soaking in rays for 24 hours. it seems to have done her good. she's looking really healthy now and growing like a beast. should i just leave the lights on until i want her to flower, when i'll switch her to 12/12? or should i do 18/6? 24 hours made her boom, but is 18 better?