If your growing in soil, fox farm or especially miracle grow I quit using nutes at all. Best grows I ever had. don't get sucked in by companies saying you have to have this or that to grow some weed, I know hydro is different but if your using commecial store bought soil its just about impossible to fix if you srcew the pooch and believe me it's easy to do. Anyone who says flushing soil will do anything but drown roots will lie about anything. Companies are getting stinking filthy rich selling unneccesary nutes to people who end up screwing up a grow. I'm serious if this is your first grow don't do anything if you are using a store bought soil like miracle grow or foxfarm. Even Fox farm nutes on thier own soil ,,, just don't need them... Try it just one time. You will probably have many grows so try this just once and see and save youself cash and headache I'm just sayin' Cheers