The water schedule is: change it completely once every 2 weeks or so. Food in the water after 2 weeks, starting slowly, building up to roughly 1200 parts per million or so (meter needed). Water occasionally with just water, or monitor reservoir PPM carefully. Change from veg food to bud food when you go to flower mode. And put lots of bubbles into the water schedule. Very important.

Oh yeah, a lot of people like to eliminate food from the water schedule during the last week or 10 days, to help get rid of any food taste in the bud.