Bigger leaves are turning a yellowish color while the smaller leaves are green.
Nitrogen deficiency - add nitrate of soda or organic fertilizer.
Older leaves will curl at edges, turn dark, possibly with a purple cast.
Phosphorous deficiency - add commercial phosphate.
Mature leaves develop a yellowish cast to least veinal areas.
Magnesium deficiency - add commercial fertilizer with a magnesium content.
Mature leaves turn yellow and then become spotted with edge areas
turning dark gray.
Potassium deficiency - add muriate of potash.
Cracked stems, no healthy support tissue.
Boron deficiency -add any plant food containing boron.
Small wrinkled leaves with yellowish vein systems.
Zinc deficiency - add commercial plant food containing zinc.
Young leaves become deformed, possibly yellowing.
Molybedum deficiency - use any plant food with a bit of molybdenum in it.