Fox farm nite help

I have 3 slh under a 400 watt mh, in FFOF and they were doing great, I started 1/4 strength grow big and big bloom, at 2 weeks (last watering) should I do 1/4 everytime? Or every other watering? I'm only vegging 1 month total (11 days left actually (time constraint) and should I give full str grow big? When should I bump up to 1/2 str, but main concern is how often to nute