Babygro if you really need to resort to insults to make your opinion seem better than anyone elses, it is apparent that you are losing this little battle of opinions. If you are wrong then you're wrong. Don't drag it out into an insult war.
The browning/yellowing is on most of the leaves, not just the top if you'd take a closer look. I know what an over watered plant looks like, it wilts. This plant is NOT wilting. It is just showing the browning. Also over watered plants ALSO start to yellow and brown at the bottom. A friend of mine deliberately over watered one of his clones as part of a test. They wilted. and then yellowed at the bottom.The most common thing that makes the newer leaves turn yellow is heat stress, but the leaves aren't cupping. and I don't think the light he has is powerful enough to cause this. Thus it is either a nutrient deficiency, lockout, or the starts of a nute burn. Since I don't believe he is using a fertilizer yet, the most probable choice is a deficiency.