yellowing and browning on my afghani high quality pics

starting to have some serious issues ive flushed her out and it just got worse im not sure if i have a defficency or a toxicity im in the 4th week of flowering and my afghan is starting to turn yellow and get some brown leaves any help would be appreciated
running canna coco with canna nute line
ph is 5.8-6.0
ppms at runoff were at 850 so i flushed and brought them to 400 using tapwater with 250ppms
400 watt mh to hps conversion bulb w/aircooled reflector
temps from 65 at night to 73 daytime 45% humidity
i water just about everyother day with 20% runoff and 1 out of 3 waterings i use nutrients according to cannas schedule

this set of pictures was taken today 4 days after the above set

anything would help please help me figure out whats going on ive been searching all day and only thing ive found is it could possibly be a sulfur or irom deficency

looking good if you ask me. maybe add some N and you should be good.

on second thought after looking at the second set of pics you do have an issue. back off of your feed for a minute it sounds like your ph is good going in but whats your runoff ph? my best thought is keep flushing for a good many feedings and then ease back to your feed schedule. try foliar feeding with light but well balanced nutes. good luck.

one other thing is problems dont correct the very second you adjust your program. what i mean is...the plant itself is sick and just like a flu may take several days to recover and basically living off water until everything is purged. over-reacting and adding things for deficiency too soon, will only create more problems especially if you GUESSED wrong.