Hi
@huyngoquang12! Indeed, your plants have burnt because of a nutrient toxicity, so from now on you should avoid any nutrients but sugar/molasses to increase the terpene profile and maximize resin production. She should be done very soon, so any NPK nutrient you add now will probably remain into the buds, resulting in poor taste and bad smoke. At this stage, focus on the flush, give it only plain pH'd water until the harvest, make sure not to flood the medium, and you should be fine. Let me know in the comments section if you need any further information, and happy growing! 👊