I'm guessing they're still in veg?
Depends on how mature the ladies are, as to how fast she'll go thru the nutes. Usually, a mature lady will exhaust the bulk of the nutes within about three weeks, but keep an eye on her, and see if she starts developing signs of defeciencies by week two. Once you do decide to start adding nutes, (Miracle Grow All Purpose?) start at half-strength, and watch for reaction. Increase dosage to full strength as the plant progresses, if there are no other health issues.

Which nutes are you going to use for flowering?
Rusty Trichome Reviewed by Rusty Trichome on . MG/Pre-Fert Soil Users: I gotta ? I'm using flower potting soil in combination with vermiculite (about 1/5 vermiculite at least). The N-P-K values for the soil are: (N-100mg/l, P-60mg/l, K-400mg/l). I just transplanted from 10L to 15L buckets yesterday, when do you think I could start to give them nutrients??? I give them water about once every 2.5-3 days, with a little run-off. Rating: 5