Who knows? Are you using a growing medium that has nutes in it? Is it just plain unfertilized soil? Hydroponic e/f setup?
You have two choices:
1) add nutrients now and see what happens
2) wait to add nutrients and see what happens
In choice 1, if you start to see your plant's leaves showing any symptoms of being overfed then go back to water (burn marks, curled tip ends, etc). In choice 2, if the plants start showing sign of being underfed (bottom leaves will start to turn yellow) then add nutrients.
I helped a buddy with his first grow and he used Fox Farm...in the blue/aqua bag. He used straight water until flowering. No signs of under nutrition. Now, I'm not saying they were the most optimal plants they could have been, but they were definately robust and healthy (well, I would have had mine look a little more green but they weren't yellow).
If you do not know the signs of nutrition status send me a PM and I'll be happy to help.
If I don't hear from you, Merry Christmas!