if you focus on one thing ,the others tend to lock out,that not even bad,matter fact you gonna have 1 long ass cola when it done,feed the soil friend not the plant,wasnt gonna say it,but cant help myself,THERE IS NO WAY IN HELL TO FLUSH SOIL PERIOD so dont make a mud pie,if you screw up in three days it will heal itself pretty much,even with a nute burn the full effect of it will be 3 days later,,i make my own nutrients and this is how i tell if i got my fermented plant juice correct,that being said,feed the soil as mentioned above and you will prevail,as far as when to stop n ,dont,add your feed were you have a higher ,p,k and keep the n side light but dont shut it off,nitrogen is in the air you and i both breath as do they,but in closed quarters we have to supplement sometimes,so in veg ,last week or two start dropping down on N and feed more p,k,once flower and stretch has stopped ,start feeding the higher p k and n at a low count and all good if you dig,you can also turn your hps bulb on last 2 weeks of veg,then swap to mh bulb first 2 weeks of flower and it will slow the stretch a lot,,im saying get on the band wagon to organic gardening all the way bro,look into KNF make your own feeds,if you dont have room to ferment,look into better organiks all organic and the brother can help you all the way,if @Ecompost cant help you at the moment,his staff is just as sharp as him,,you can even pm here on the farm if you need help,the brother has a huge farm and it is planting season were he at so give a few days and he will answer you ,or just go to site and check it out his staff is always there to answer and solve problems