i'm on well water and the strain i'm running now is the first Ca deficiency I've ever had since using all well water and Maxibloom. i normally supplement with just Epsom for Mg and Su but this is the first time i've used my cal/mg bottle in a long time.
I have a strain of UBC Chemo from several years ago that prompted me to have to add in calcium. I pull water from a lake, and no other strain I've ever grown has required it except that one.