I know this is a old thread but I would to share my current experiences for anyone who stumbles across this thread through a google search as they are racking there brain over sick sad plants...
I have been using cogos original nutrients for my last grow and was using it in my current grow until yesterday. Plants have been in veg for roughly 5-6 weeks, I was going to flower until this problem manifested.
The thing is with this nutrient, when I mix per there instructions the ph is VERY VERY LOW, I am using RO water from a stealth 150 and water comes out at 15-20 ppm, I have to use allot of ph up (potassium bicarbonate) to bring it up and the higher concentration of nutrient I add, the lower the ph gets and more ph up I have to add, plants looked hungry so I bumped them to close to there recommendation and added the up as usual (quite a bit is needed of course). Next day first sign was plants where flaccid and weak resembling text book under-watering, so upped my water schedule (hydro). Plants seemed to respond well the next day the following day it was back and now accompanied with deficiencies (dark purple leaf stems, purple stems and leaf curl downward, I immediately drain res and fill with ph’d water and h202 for 2 days and drain and fill back with 1/4 strength nutrients and plants are doing much better now and starting to recover as I have changed nutrients. damage is done of course, plant leaves are twisted, wrinkled, deformed and a little necrosis signs of definite calcium, magnesium and iron deficiency I am convinced that the potassium bicarbonate ether added far too much K which caused a toxicity and locked out these very important elements or it peaked the salinity of the mix causing salt stress and essentially nutrient lockout in general.
So just a heads up for anybody seeking info I absolutely believe (plenty of tests of high salinity feed water effects on plants) that sodium bicarbonate, potassium bicarbonate and potassium silicate used in large volumes definitely has negative effects.