Nope .....not unless your a die-hard organic grower that uses teas for everything......I use plant magic cal/mag every feed and it's never gave me any concerns(no need to flush)tast is 100%....I've recently switched to a cal/mag called DENSITY it has more trace elements in it but this is my first grow using it and so far it's looking good.....Yea the product you have will be fine......your plants r looking well the pistils you r quickly seeing r because of the amount of time you vegged.......that plants going to be massive by the time it's done mate so make sure your space is big enuff for it.......
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I am nearly done saving for the kit I want, hopefully 1.2x1.2x2 meters should be enough! Will give a dose of calmag tomorrow or Friday depending on how dry my soil is!