I feed mine 1 tablespoon ES to gallon of water once a month.

Thanks, Marquest. That's exactly what I needed.

put some dolomitic lime into the soil and it will release adequate magnesium slowly for many months

dolomite can be found in home depot, it is very cheap, a few bucks for a huge bag

the problem with epsom salts is that they do not last in the soil so the plant has a brief period to absorb it, whereas with dolomite it is constant