Technaflora B.C. Hydroponic Nutrients Boost - 4 Liter

So just to be sure this is not the main fertilizer it's just to give it a boost for the flush.do you have to flush on tomatos?

What is the difference in the bc boost brown/A and the other bc boost with different labels?

why is it $41.49/gallon, but if you sign up for subscribe & save you get charged $47.50 before discount & tax?...please fix that