it could help if you still got like a month or more i dont think it would hurt them at all. just when you get ready to harvest them flush them really good.
i know this is late but i would have put them in a bigger pot its like a gallon a month soo yea and it looked like they needed more nutes ... and if it were me i would have clipped some of the lower branches also that way theres was no wasted nutes. and the light i would have moved to about...
i wouldent use MG id use happy fog and fox farm mixed with about half a bag of Bat guano its works the best like that and you dont need to use nutes in flowering if you do it that way with 3 gallon pots 1month in veg. 2 months in flowering.(if you use HPS in flowering).