Pump some iron!
A highly concentrated (10,000 mg/L) ferrous iron (Fe2) gluconate. Nitrate and phosphate-free.
What it does:
Brings out vibrant colors in plants and vegetables. Helps to prevent yellowing. Use where additional iron is needed to prevent iron deficiency, or where signs of iron deficiency are present, including weak thin stems or yellowing between the veins of the leaf (chlorosis).