Leaves are dying off, gone dry and crumbly, and stems have gone very pale

[Jada]

Help me please!! I am a first time grower, I went down 2 days ago to feed my plants, I use Lets grow A and B, powerthrive, and canna boost, also use ph up and down to control ph level. They fed fine, looked great, got the levels to 6.5, then last night I went down and the leaves on many of the plants have withered, (I fed them a little bit extra the night before as I had difficulty gettin Ph down) I have gone down again this morning and most of the leaves if not all have withered, turned pale green and are crumbly to the touch. The stems also look pale and so do the buds, They are currently in week 3 of flowering. I* have had spider mite which have been treated with predators and controlled well, I dont use any other treatments or food. Looks like my whole crop is dying! I use a large tent, have 2 fans, also an intake and outake, the temp is maintained at 28 during lights on and down to 22 when lights are off. Its feeding day today but I am not sure what to do?? Do i flush them or feed them as normal?? I am a complete novice, learnt everything i know off DVDs and websites, and with a crop of 20 plants I really dont want to lose them! Sorry no pics as camera isnt good quality! Any advice would be appreciated!
Thanks guys x

 

[jvilla]

to me if the vains in the leaves are yellow and stem is a little purple and wasnt before(some strains have purple stems) its a mag problem gets some cal-mag or and some shooting powder by house and garden. start there wouldnt hurt for some magic green for a foiler spray

 

[marski420]

Number 1. How much is "a little bit extra"
Number 2. What kind of lights/ wattage are you using and how close are your lights

It sounds like your crop could be toast.. If almost all leaves are crumbly to the touch thats not good.. That happend on my first grow. My plants were in veg when I did it, it was a mixture of over feeding and taking away my flurocents and putting my 1000W on them.. which at the time was mid summer and I had no heat control. Also my humidity was VERY low

If anything is the same let me know

 

[OZUT]

to me if the vains in the leaves are yellow and stem is a little purple and wasnt before(some strains have purple stems) its a mag problem gets some cal-mag or and some shooting powder by house and garden. start there wouldnt hurt for some magic green for a foiler spray

You definately don't want to add shooting powder. You'll kill them for sure. You use that stuff towards the end of the cycle and only on healthy plants. It's something like Phospher load.

Now you said you got PH up and down but had a hard time getting the PH down. Do you have a meter and is it calibrated? First thought is you over watered them which is why they probably wilted. You fed 2 nights ago and fed them a little extra, then you fed them again today and you're considering feeding again. I'm assuming you're in soil. But then you said they're crumbling and the leaves are pale. I think you have more than 1 problem.

Try raising your lights, and letting the soil dry out for a couple of days. Not knowing what size pots you're using, but with a 3 gallon pot and 3 weeks into flower, you should be watering once every 2-3 days, depending on different variable.