Just so you know, a calcium deficiency and a magnesium deficiency are two different things. BC cal-mag has both nutrients in it, people often refer to the deficiency as a "cal mag" deficiency.
But for future reference (and to get yourself one step closer to being a pro), remember that a calcium deficiency usually shows up as either yellowng around the perimeter of the leaf, or brown spots on the tips/ outside ridges of the leafs (or just brown spots on the leafs in general), while a magnesium deficiency generally shows as a yellowing leaf, but with the veins of the leaf still green, so just the leaf "margins" turn yellow.
You might have really soft water, usually tap water has enough calcium and magnesium to sustain plants that small. If you can, get a tds meter and test the parts per million of your water. If the ppm is below 150 then you should treat with cal mag every time you water and bring it up to 150 ppm.
