Feeding the pot-growing citrus trees

The 4 citrus growing on pots are looking very yellow so we decided to given them Greenall F.S.T. (Iron and Sulfur). The instructions advise to give 1/2 pound per container so that is what we did. The F.S.T. was puored on the surface of the vases and them mixed with the top soil. After that, we watered the pots until the soil was soaked.