Ok.. so i'm noob at this, but from doing a lot of research before i started, i am assuming this is nute burn. I'm using logic to make this assumption, as this is the only plant that has discoloration and it's only on the second node of leaves, and only on that one for that matter... I did scale nutes in the past two weeks, very small amount the first week, scaled up a little this week, just showing discoloartion yesterday.. now the leaves look as if they might die off. No biggie, the rest of the plant is healthy.. i just want to make sure this is nute burn, and that i caught it in time before it spreads to the rest of the plant. Also, i questioned airflow, but the box has constant air circulation, all leaves lightly move.