Unfortunately, it's not that simple... You would need a ppm/ec meter to properly flush and know when to stop flushing.. You need a ppm/ec meter whenever you are using a nutrient line.. That's what tells you how strong your feed or mix is.. Your plant is in flower, so it will not make any new leaves... (That's what veg is).. You can only try to stop/slow the spread. Before any recommendation can be given, we'd need all of your detailed grow info.. Your nutrient line, how/when you feed.. The ph of your feeds.. The ph of run off.. All the basics..