[juikelin]

hi all. i've heard that epsom salts are good for tomatoes,
     is this right, and how much and how often. I'd apprieciate
      any advice. thanks.

[mumofstig]

Epsom salts are only useful if your tomato leaves are showing magnesium deficiency.
This link mentions high-tunnels, but the advice is the same for outside.
https://extension.sdstate.edu/monitoring-and-correcting-magnesium-deficiency-high-tunnels