You should be worried about light coming in the tent not out. As long as you do not have lights on all day long outside the tent there is nothing to worry about
I run mills as well. Are you using there full line up?
Mills has cal and mag already in it.
I use there medium feed chart and hand water. I do not test ec so i prob am no help but i love there full line up so far but definitely pushes the n to the limit.
Heres my grow at day 29 of veg.
Your not joking about that they deleted so many of my threads saying i cant put facebook or instagram qoutes in the thread and i dont even have facebook or instagram lik wtf.