Lamp burn or nutrient burn?

So, here is what happened on one of my leaves:



Not sure to what's it's due, so I'd appreciate any input / advice / opinions.
It started to happen on another leaf tip, but hasn't developed more.



Thoughts?

its seems to be the lower part of the plant so why do you think its the light if the upper part of the plant is ok? explain your reasoning please. Post more info , room temps etc, but it looks like you got a tiny either calcium or nitro deffeciencie

True, it's not the very top of the plant that seems affected. However, since I'm vegging with 4x 30w CFL's, one of them was hanging very close to that side of the plant. That's why I initially thought it was a light burn.
But then again, I'm not controlling PH yet, so it could also be that (I'm using a soil mix & hydroton).

Looks like light burn to me