here's something I posted recently:
Calcium (Ca) deficiency can cause new leaves to distort or take on a hooked apearance, growing tips may also die off.
Nitrogen (N) deficiency generally causes older leaves (bottom leaves) to yellow with remaining foliage turning light green. slow growth and yellow spindly stems also.
Magnesium (Mg) deficiency can cause slow growth and cause leaves to turn pale yellow with new growth being yellow with dark spots.
Phosphorous (P) deficiency can cause leaves to take on a red/purple tint. leaf tips may look burnt with older leaves looking nearly black. fruit and seed production is reduced.
Potassium (K) deficiency causes older leaves to look scorched around the edges and possibly wilted also. yellowing between the leaf veins may be evident.
Sulphur/sulfur (S) deficient plants have new growth turning pale yellow with older growth remaining green. plant growth is stunted.
Boron (B) def. may be evidenced by poor stem and root growth, buds die off, a 'witch's broom' effect may sometimes form.
Copper (Cu) def. causes stunted growth with leaves becoming limp, curling or dropping off.
Manganese (Mn) def. causes slow growth, younger leaves turn pale yellow often this discolouration starts between the veins. dark or dead spots may develop, reduced size of leaves and fruit and failure to blossom.
Molybdenum (Mo) def. - older leaves yellow with remaining foliage turning bright green. leaves can narrow and become distorted.
Zinc (Zn) def. causes interveinal chlorosis (yellowing between the veins) of new growth. end leaves may form a rosette.
foliage discolouration can also be caused by soil that is too wet and/or poorly drained or soil that is too compacted inhibiting root growth. those growing in containers or those having a lot of clay in the ground beware. too much fert is also very bad, many growers kill their plants with kindness. too much fert will cause plants to look scorched or wilted even though your watering regime is adequate.
