Yellowing leaves

Having put my three girls into 12/12 just around 2 weeks ago, I have noticed that quiet a few of the older and lower leaves are turning yellow, and the leaf stems are turning purple, is this simply a nitrogen deficiency perfaps due to build of salts in soil, or as a result of the plants chemistry changing, I know these lower older leaves act a N resevoirs so could it just be that the plant is redistributing its Nitrogen? Or could it be anything else? Perhaps this is normal!! Any comments would be welcomed, especially if you have an answer.

Thanks in advance

a few ideas come to mind, 1st it could be like you said and you have nute lockout due to a buildup of salts in the soil, try flushing them with twice the amount of water of the size of your containers...{taken your growing in soil}then add about 10 caps of 3%h2o2 to a gallon of water and add your ferts. the h2o2 will super oxigenate the water. i add h2o2 to every drop of water my kids get it helps super stimulate root growth making for super healthy plants! another thought is....how cool does your room get when its dark? low temps will also lock out nutes. given the time of year, and the purple stems that could be it? id have to know a little more about your setup before i could say for sure. btw what kind of nutes are you using? let me know if this helps peace

Hi, and thanks for the advice, I found the problem However, it have been using Canna vega during the veg period, when mixed up with the water this feed retained a PH 6,5-7, However when I started the 12/12 I switched to Canna Flora and foolishly asumed that the PH would be correct, however after checking I found that the PH of the Flora feed when mixed was PH 3.5-4! so lesson learned, I flushed the soil with balanced water then fed with a Feed of PH 9, this brought up the PH of the soil nicely, I checked the run off after a few feeds and things are now balanced again! And I have noticed a that the buds have really taken off, I lost quite a few of the older leaves but to be honest they were so bushy before that a lot of the buds were getting no light, so its not a bad thing. All in all they have grown about 8-10 inches in the last week, and I have counted 26 buds on 1 plant, 23 and 27 on each of the others, the biggest being around 8 inches long, so hopefully and I reckon around another 4 weeks, I should get some first class smoke!, I will try to post a few pics when I get chance.

How much light are you using to grow your girls????

I used 600W HPS during Veg and now using 1200W hps (2x600)

They should be ready in around 3 weeks

be sure to post what your yield comes out to :) :) :)