lower leaves starting to turn yellow and go crispy

our plant over the last week (week 7, week 3 flowering) has started to get yellow leaves near the bottom that are quite dry too. i looked here and various other sources to find the problem which a lot of people said was a magnesium defficiency but then read that other problems can cause this situation so i thought id post pictures and see what people thought. since week 5 we've been using nutrients specially for flowering stage which are the following: every 3 days using nutrients that consist of 1.5 : 1.4 : 3.1, and every 5 days using nutrients that consist of 0 : 8.5 : 6.2. i hope this is enough information to help find the cause.

what ph are you running? r/o water or tap? could be a lockout or ph problem or over /under nutes ...... need a little more info sorry

ph has been around 6-7 (perhaps too high?) been using tap water but leaving it for couple of days before using it (read somewhere that should be fine)

id go for a ph no highter then 6.5 .. causes lockout of needed nutes ... i'm not sure about what nutes your using but they do look hungry not burnt ... kinda like its taking the nutes its not getting from itself ...

very so very much toooooo high should be between 5.3-no higher than 6.3

how do i lower the ph? (first time grower by the way if you couldn't already tell)

get some pH down from the local hydro shop , or the old way is to use white vinegar or concentrated lemon juice ... you do have a ph meter dont you ?

got a ph meter ye just never bought any ph up or ph down from shop, thanks for help, hopefully see some improvements in the next week

remember just a drop or 2 at a time to change ph .,.... you will get the hang of it

Yo man, some links i always use

Ph in coco- http://www.420magazine.com/forums/hydroponic-gardening/76197-what-ph-do-you-use-coco.html

http://forum.grasscity.com/absolute-beginners/218218-updated-beginners-guide-ph-marijuana.html

general deficencies - http://www.marijuanapassion.com/forum/showthread.php?t=54277

http://www.marijuanapassion.com/forum/showthread.php?t=54233

lots of more in depth reading on deficiencies ---- http://www.gardenscure.com/420/plant-nursery/107527-revised-complete-guide-sick-plants-ph.html