Too much or not enough?????????????

Hi i have the dreaded brown leaf/dying leaf problem which i thought was nute burn but the friend who i got the plants from assured me he was feeding 30ml of A and B Canna Coco and i was feeding them 20/20 would me feeding them less cause this to happen?
They are in my basement and only had fresh air when the lights were on but i have changed that to 24/7 on the air and they do look a little better,could air have been the problem or sorry the lack of fresh air been the problem.

Any help will be much appreciated.

How hot and humid is your grow room ? and your ingoing ph and outgoing ?

Hi the ph is about 5.5-5.9
the room is now 25/26 at the top of plant,i was having problems and it 30 ish for a few days,dont know about humidity but will go and get a meter now and let you know