brown leaves help needed

hi guys this is my second grow could do with some expert help..
im on 12/12 under a 250 hps in to 5 weeks on durban poisen..was on canna flores full strenth and 6 ml hammerhead, but i am just watering now coz i thought maybe it overnute..i have been doing a lot of reading on the net and keep coming up with cal defficiancy..have good air supply in and out water every 3-4 days when needed.and ph is 6.7 in soil..i hope somebody can help me..thanks in advance...

well its nutrient def for sure do you ppm your nutrients?make sure you dont burnem

ppm my nutes.. now im lost..do i need another meter..ive given them a good flush and ph is 6.7-6.8..i hope i dont lose my ladies, on the last 3 weeks now..i getting rather concerened..dont seem to b getting no worse,all new growth is green its only 2 out of 12 so i lost ..does that mean it working its way out..these ladies worse than the mrs and me 3 kids..lol..thank you for all help..its much appreciated..