Hey Eric, I would say it wouldn't be a bad idea once in a while to boost with calcium nitrate, but not absolutely necessary with MSU. Epsom salts, yes, absolutely add more magnesium periodically, especially for roths and any Paph you start to see that brown leaf tip die back with a yellow leading edge, the stuff you cut off and it starts right back up regardless of what you treat it with.
I think I'm sold on this whole Epsom salts deal. Where should I pick some up? Is there any chance the drugstore stuff is ok?