Cal/mag contains calcium and magnesium, and no nitrogen at all.
If you are concerned with the yellowing, adding some nitrogen to your feeding schedule will help and this can be as simple as giving half grow and half bloom nutrients a couple of times, instead of just straight bloom nutrients.
Different plants will have different requirements, so what may be fine for one could be either too much or too little for another plant.
Even two plants of the same strain can have different requirements.
Hope this helps, Organoman.