Here's a quote from the link and save this link for future problems.
Â
"Iron plays an important function in the production of chlorophyll and enzymes. Deficiency causes stunted growth in chilli plants and is characterized by interveinal chlorosis, or the yellowing of leaves whilst leaf veins remain green. Affects the new growth. Chlorotic patches appear first but these can grow to cover the whole leaf. In extreme cases, leaf tissue becomes completely white.Â
There is usually sufficient iron in compost or soil for your plants needs. Iron deficiency is more commonly caused by a lock out of nutrients With iron, this could be high soil ph, high temperatures or excessive phosphorus in feed. Check and adjust as necessary.Â
Iron deficiency can be treated with chelated iron, commonly available in garden centres. Foliar spray at half the recommended dose. You will see the green start to flush back into leaves within a few days and, apart from any completely white patches, leaf tissue will completely recover. Be careful not to overfeed with iron as this can in turn can lock out phosphorus."
Â
https://www.worldofchillies.com/growing_chillies/growing-tips/chilli-plant-nutrient-guide/chilliplantnutrientguide.html