Start feeding it at 3 weeks (unless you repot it, in which case leave it for another 2 weeks... that way, the plant will have used up nearly all of the nutes in the soil). Remember to start feeding it at quarter strength, then slowly build it up. Watch the plant to see if it likes it or not aswell. Some strains dont like being fed nutes, as I found out with the WR. Ill update me growlog sometime soon, shes stretching like a whore on crack and she didnt like the spunk I fed her...