When brewing tea, you only add what doesn't dissolve well in water. Ferts that dissolve in water don't need to be made into a tea. If you add them while brewing, they will saturate the liquid with nutrients and make it harder for nutes from the solid ferts to dissolve. Once a tea is brewed, you can then add easily soluble ferts to adjust the nutrient ratios. Some of the best fertilizers are mixes of a few different substances.