Yes, if you look on the label of the Epsom Salts, it is magnesium sulphate. Very soluble and plants love it (not just orchids). Magnesium is an essential nutrient for plants to make chlorophyll which is the green stuff in the leaves that collects the sunlight.
The orchid books I have recommend using fertilizer with a low middle number (low Phosphorus) but that is specifically for Florida where we have phosphorus naturally in the water. What I'm using right now is a formula with a nutrient analysis of 14 - 0 - 46 and it sure has done wonders for my plants since I changed from a "regular" orchid fertilizer. The old one had 20 - 14 - 13 and the Bloom Booster fert has 20 - 35 - 15. My orchid book doesn't recommend using the bloom booster formula except maybe once in the spring and once in fall.
