What strain is it? Is it in Veg or Flower stage? If in Veg, for how long? If in Flower stage, For how long? Indoor or outdoor? Soil, Soilless or Hydro? If soil/soilless, what is in your mix? If soil/soilless, what size pot?
Size of grow space (LxWxH)? Make and model of grow light? Temperature in the environment? Humidity in the environment? PH of medium or reservoir?
PPM of medium or reservoir? Any Pests? How often are you watering? Type and strength of nutrients used?
Lots more info needed. See this post to see what you should include: https://www.mrgrowit.com/forum/grow-community/read-me-first
What strain is it? Is it in Veg or Flower stage? If in Veg, for how long? If in Flower stage, For how long? Indoor or outdoor? Soil, Soilless or Hydro? If soil/soilless, what is in your mix? If soil/soilless, what size pot?
Size of grow space (LxWxH)? Make and model of grow light? Temperature in the environment? Humidity in the environment? PH of medium or reservoir?
PPM of medium or reservoir? Any Pests? How often are you watering? Type and strength of nutrients used?
more than one. maybe 6-12
Is it just one leaf? And don't think the top dressing did it, not that fast.