They probably won't need much at all if you are growing on ocean forest mix. Most peeps could avoid burning their plants if they simply started with say a 1-2 gal pot & then went up to like a 5 using fresh mix. Then go to a 7 or 10 gal just before bloom & then maybe they will need cal mag and some extra npk during mid to late flowering but that's about it. I say water only for as long as you can. If you see them lightening up go to a bigger pot or hit em with low dose of nutes. Don't wait for yellowing wait for light lime green then feed.