inkcube

the fert you bought should be fine.

any fert including cabbages leaves, compost, or coffee grounds will lead to salt. a salt is the product of a chemical reaction. epsom salts are magnesium sulfate (MgSO4·7H2O), a SALT, and should never be put into the pot, as crystals - they will burn roots. also if you water too much with epsom salts you will cause an imbalance of other micro-nutrients in the soil such as iron, manganese, zinc, and copper - i have seen a lot of growers (home & commercial) damage plants using epsom salts too frequently. they compete for the same binding sites in the soil and on the roots - the element in the greatest concentration generally gets all the binding sites. also never mix the epsom salts with your fert or you will negate the benefits of the fert, adding too much Mg which will compete iron, zinc, manganese, and copper deficiencies possibly causing them to "fallout" of solution and not being available to the plant.

for what its worth, calcium deficiencies do not show up often unless you have high alkaline soil - plants take up Ca easily especially in peat-based mixes. if you sprayed any insecticide; natural or man made and subjected the plant to full sun or strong light you will get burning on the leaves. in the greenhouse we spray very early in the morning ~5:00-7:00 am so the chemicals are dry by the time the sun is at its strongest.

too leach your soil pour a volume of water through the pot that is equal to the soil volume of the pot.