Despite decent Ca levels as written in the tittle i still have severe burned and stunted tips on my Umbrosum and Alternatera reineckii. Those symptoms go away when K is almost 0 ppm but at the same time K deficiency shows up (at 0 ppm K plants begin to grow healthy in only 3..4 days time). Many say that the problems with stunted/burned tips are due to low NO3, CO2 etc. but i checked all that stuff and i can say that is NOT the case; it didn't helped at all. I tried high NO3, high PO4, Mg, changed micro ratios and levels (the only micronutrient i didn't change was copper but i don't think it would have any effect) I also tried low levels of SO4, Na. I wonder HOW some of us can have high K and low Ca and no problems i've just written about. If there is someone who can explain in simple words what causes such issues and it really helps he should be given "Planted Tank Nobel Prize"