You asked a question earlier about some discoloration which was causing yellowish brown section on lower leaves and you pick a answer rmyo that question but I don't think he was on the right track I think you have a phosphorus deficiency
First, balance pH (Hydro: 5.8, Soil 6.0 - 6.9) or re-apply nutrient mix if necessary.
Organic Solutions:
• Bat Guano
• Bone Meal
• Crab Shell
• Crab Meal
Inorganic Solutions:
• PK Boost Supplements
• Phosphoric Acid (Soluble Phosphorus however raises pH quite a bit)
Good luck
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