Foliar feeding with Epsom salt is almost as good a wifes tell as plants loving to have all the fan leafs plucked off. If you have a cal def, then either use tap water or go buy some cal/mag.
The other one I love is when someone says, "You must let your water sit for 24 hours to allow the chlorine to evaperate off, or you will kill your plants". Then in another thread, that same person will be telling someone to add chlorine at 20 times the amount of tap water to get rid of algae.