I've watched the weed nerd for a while all Sub uses is pH balanced RO water during veg there is mycorrhizae in the soil so there shouldn't be any need to add more but if you look at the N-P-K on their website the soil is lacking in potassium so they recommend feeding your plants a carbohydrate source during flowering like Humboldt Honey which has potassium in it and provides the plants with an organic source of B vitamins and amino acids