More details might help. Some upright photo's and maybe grab some shots after lights out. Your photo's are over saturated. I noticed lots of people have looked but no one has said anything. Personally not done diesel but it could be any number of things. What is your RH. How many watts is that light how close. The other plants in the background don't have the same trait as far as I can tell. Maybe just a mutant. Did you maybe give that one to much water. Can't tell if you are hydro or soil. Any other problems besides the very top leaves curling. Looks like the leaves below look normal. Hard to say without better shots and details.
Looks to me like stereotypical nitrogen toxicity. Cause by either too much N or not enough light.... Or a combo of both.
I have a plant that looks just like this ATM and reason being is that the majority of her is growing past the light.