What did i do? what do i need to do?

i have 15 plants its the only one like it. there are a few others with lower leaves that are browning and are crispy. i just put them under a 1000 hps today. before that they were under a 400 mh. they are in 4 in pots and i will be putting them in 3 gallon bags tonight.

water it dude!!

I have been. i have been watering it with plain tap water that i let sit out for 24 hours and 1/4 strength mg every other watering.

then i got no other answers, sorry.

how far away is the light.. how old r they? they look too small/young to be giving fertilizer.. and u should steer clear of miracle grow. (its a miracle IF they grow)
try raising the light up and giving that plant a flush with some PH balanced water..

or just read some of this and see if your symptoms match up to something in there.. it should be in there

The Complete guide to Sick Plants,pH, and Pest troubles!

Dertmagert and the complete guide strikes again. True piece of gold you found there.
Looks like it needs water...if you use anything at that stage it should be SuperThrive, and just a little bit of that.

it is about 2 feet above and the bulb is like 67 more inches higher. they are about a month or a month and a half old. im going to get a ph test kit. i was following a book by jorge cervantez thats where i was told to use mg.

6 or 7 inches higher sorry*

I checked my PH and it is 7.6 how do i lower it and what should it be at?

lower 5.6-6.0 is wat i keep mine at

use a base. mix some in with your water that you use to water the plant, or just get some distilled water. that'll make the pH go down some.