Hey man, i eventually solved this problem by switching to general hydroponics 3 component nutrition, one of the 3 components has all the calsium and magnesium i think, so what i did was using like 20% more of that one component than the others, after that the plants grew without any problems. I also bought a air humidifier wich also helped alot.
I will only be using general hydroponics nutritients with my led grow lights from now on, simply because of the way you can change the nute mix perfectly when you got 3 components instead of two like with canna.
