Can be caused by:
• Improper pH
• Nutrient Lockout
• Out of range VPD
Flush your plant and reapply accurate, balanced nutrients
Before adding supplements to a plant's root zone, check the pH level of both the soil and/or the water solution (especially hydroponics) for plants. If the pH is high then it can be helpful to buy and carefully use a sulfuric acid-based fertilizer to both re-introduce sulfur, as well as bring down pH levels.
If pH is within a normal growing range (5.5 to 7.0) then using Epsom salts would be a good source of sulfur for watering/hydroponics.
In soil-based grows or outdoor grows the use of gypsum is good for sulfur introduction, but you may also use sulfate-based fertilizers such as ammonium sulfate or calcium sulfate, among others.
If you have access, manure could be a great organic option as well.