Adding minerals to your soil.

http://www.traceminerals.com/products/liquid-tablet-minerals/conce
"Gardens and Plants–A study done by Rutgers University and other studies done by the USDA noted the severe mineral imbalance and depletion in American soil. For years many avid gardeners have used ConcenTrace® on their gardens as well as in the flower beds. It is also very beneficial to house plants when diluted with water. See the difference in your plants."

So can this be used for cannabis?
I have a ton of this stuff.

It's for people but I guess you can use it but you will need to look mat the requirements for each of the elements to see what concentrations to use.

A little Azomite added should do fine. Kelp meal or a liquid form will work too. You might have to add kelp several times, but if you buy any you should have enough for several doses.