Sulfur is a secondary nutrient, essential for the formation of proteins, amino acids, and chlorophyll which is part of photosynthesis. Symptoms of sulfur deficiency present as pale green and yellowing leaves starting in new growth throughout the plant, as it's a semi-mobile nutrient. Necrotic and drying spots throughout the leaf, the edges, and the tips. In severe cases, the plant's growth will be stunted and spindly.
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.