Potassium dificiency - add muriate of potash. Cracked stems, no healthy support tissue. Boron dificiency - add any plant food containing boron. Small wrinkled leaves with yelloish vein systems. Zinc dificiency - add commercial plant food containing zinc.
Young leaves become deformed, possibaly yellowing.
Molybedum dificiency - use any plant food with a bit of molydbenum in it. Like most other things in life, the amount of good you are going to do relates directly to how much effort you are going to put into it. The grass will develop a mold which tastes a bit harsh, and burns a tiny bit funny, but does increase the potency. Expose the grass to the high intensity light of a sunlamp for a full day or so. Now carefully boil the mixture on an electric stove or lab burner.