Magnesium – For making chlorophyll for photosynthesis, without it, the leaves will turn yellow and suffer stunted growth
Nitrates – Provides nitrogen to make amino acids for protein and growth. Without, poor growth and yellow leaves
Potassium – Respiration and growth. Without, poor fruit and flower growth and discoloured leaves
Phosphates – Respiration and growth. Without, poor root growth and discoloured leaves.