conifers and moss prefer acidic soil 5-6ph, but cannabis in soil prefers 6-7ph. You might be better off digging those up, washing off most of the existing soil, replanting in a good store bought planting mix in 2 gallon pots before putting them back in. . some guys use jacks citrus blend powdered nutes for a simple solution. ideally you would see how they respond to the new soil, then add nutients in a few weeks if they need it, if you get a good mix you may not need any.