Probably won't damage them, Toni. Depends upon the size of the plants of course.
Some people do just sprinkle the undissolved crystals randomly on the ground around the plant, but my tomatoes are all in containers so I don't like to do that. But if you think you overdid it, just hose them down really well, because the Epsom Salts is so soluble it will wash through very quickly.
With tomatoes, it's pretty hard to give them too much of anything when they're on their big growth spurt in late spring. I have a plant in an Earth Box right now that has to be 8ft. wide and 6ft. tall, sprawling all over the place. Another month it will be finished for the summer as our hot nights prevent them setting fruit, but right now, it's a MONster.