Like developing children, plants also constantly need calcium and magnesium for strong healthy growth. But even experienced growers often overlook another element plants need, specific forms of iron in proper proportions. If you are using low quality basic fertilizers, your crops may be deficient and therefore have stunted growth and yellowing leaves, in which case you need Sensi Cal-Mag Xtra, the only calcium and magnesium supplement formulated with the exact proportions of Ca, Mg, e Fe. It also contains the optimal amount of the various necessary micronutrients.