Hello @Leeguan. That is a wind stress / burn. It is very common amoung growers to be confused with nitrogen deficiency. Move a little further the fan ( that i can see in your photos hitting the top of the plant) and you wiil be ok. Happy growing!
Hi @Leeguan! What you're having here is a Nitrogen Toxicity, also called "the claw" because top leaves usually look like a bird's claw (curling downward). This can happen because of too much Nitrogen in the feeding solution - of course, but this can also happen if the plant doesn't get enough light to "transform" the nutrients into energy. Now as a solution, I'd recommend to stop nutrients now and until harvest. Nitrogen toxicity is known to give a very bad taste to the buds, so it's important to start flushing as soon as you can. If you can give this baby more light and less nutrients, while controlling the day&night temperatures, she should be fine. Hope this will help, keep us up-to-date and happy growing 👊
Hey leeguan are you able to give any specifics on how much and the exact lune up of the biobizz? I mentioned going to less than 1/2 strength, but you may also want a good flush done and then resume nutrients at a lower dose. Along with other possible problems. But i see your buds, so youd definitely want to be going down on any "grow" nutes and up on the "bloom" nutes. ✌️
I don't think it's nitrogen toxicity because the lower leaves don't appear to be curling at the tips, I'd say it's heat as the top of the canopy is being affected most..