Experienced growers have said their biggest jump in growth happened after installing a Dosatron.This dosing unit feeds a measured  amount of nutrients to your plants each time you irrigate. Connect a water supply line to the unit and another line going to your garden( garden hose works fine) then drop the suction hose into a container of liquid nutrients. This is powered by the water flowing through it, picking up small amounts of your fertilizer and injecting it into the irragation water. You can use any fertilizer that dissolves in water.