Epsom Salts = magnesium sulphate

Magnesium is essential and its lack can be seen as yellowing of leaves as it is in chlorophyll. Small quantities can be very beneficial if it is low in the soil. But it is a very specific fertiliser and not a panacea.

If your plants aren't yellowing then they are getting enough from general feed (magnesium is in tomato feed). It is potassium/potash in excess that fruiting vegetables really need, which is also in proprietary tomato feeds.

What a trusting soul you are Hank! Agree with Buddleja's answer - bear in mind people choose to believe all kinds of stuff. Maybe he had brilliant results when he used it on something that actually was suffering magnesium shortage, and now believes its brilliant for everything and anything, I'm constantly amazed at what people believe, often without any scientific evidence at all, or because it said it in the Daily Mail or the Sun ... still, keeps me interested in life;-))