On the big plants I discontinued use a while back even tho it's (supposedly) safe to the 4th week of flower,I think the roots are just massive trying to take care of all the upper ..I've been feeding twice a day as much as I can and try to keep lights out while I'm at work so I have more time with em,feed in the evening and before I go to work,light are on after I leave for another 7 hours,,,