Yeah...speaking of topdressing your soil...you may want to get some lime and have it for when you need it and you very likely will in MG products. Keep a close eye on ph as well.
I use a good organic potting mix and try to find one with good ingredients like feather and kelp meal, oyster shell and guanos, and then throw in about 25% coco coir for a better soil structure. I do amend my base soil with some earthworm castings but that's it. But like bkbbuds says, learn and apply. Not telling you how to grow your weed, just telling you how I grow mine.