To supply your plants with iron, try spraying liquid seaweed or chelated iron . Calcium is present in gypsum, lime, and oyster shells. Boron is available in borax and a chelated boron spray. Gypsum and flowers of sulfur are good sources of sulfur. The others are available in chelated form, usually as a spray.
Older leaves turn a pale green and the veins are usually a reddish color.
New growth will be stunted. Will look almost like magnesium but here the leaf will be twisted. When it is deficient, dead areas appear in young growth and the tips soon die. How often to Fertilize I prefer to feed each time I water, but you can fertilize weekly, bi-monthly, or every other time you water. Click here for more information.