yosemitesam imo is absolutely right about the ca. garden lime contains ca/mg ratios at 2:1. the best ca/mg ratio imo is 10:1, not 2:1. pure ca lime used for ca, garden lime (dolomite lime) as mg( not ca) supplement. ca is not just a supplement. it's a pivot point catalyst that determines what level of nutrients the plants can uptake.
completely untrue...
most use it at 100-120PPM, which I find is not needed. also really not needed beyond the point of flowering stretch
I have used Ca at 35 PPM and was one of my best grows to this point.