Good question GrandMan, really depends on the soil you bought and how enriched it is. So for example the soil i'm using the label says it's enriched for 8 weeks of feed, but commonly you'll find soils from anything from 3 weeks to 8 weeks. In your case though the size of the pot also really matters, smaller pots will lose their nutrients faster when you water and as the plants eat up all the juice. I'm pretty sure you can start feeding in week three with no fear , just dont go overboard, and make sure the plants dont get root bound for lack of space. Hope this helps ! 🚀