In my opinion, never if you stick with a consistent transplant process with the soil you are using. When they get transplanted, they essentially get fertilizer and buffers until the next transplant 4-6 weeks...and so on. I only use (now) molasses in the finishing stages.

You fertilize in this wonderful soil and you risk over fert.
WashougalWonder Reviewed by WashougalWonder on . When to begin adding nutes? When should I start adding nutes after seed sprouts? Also Just bought a "Grap Ape" clone 3 days ago, has been in FoxFarm OceanForest soil for 3 days, no nutes, when should I add nutes to the clone? Rating: 5