Epsom works great with tomatoes. I have had all kinds of problems in the past with Hydroponic tomatoes and have found that if i mix some salts with water and spray them and add some to the water or coco it works great and helps all kinds of problems.It helps with blooming, end rot, and brown leaves. You can buy a bucket at Sams club and the directions are on the bucket on how to use it for plants
I put a 1/4 cup on my coco coir per plant.Mix about 2 table spoons to a quart of water and spray. Or add some to your deep water system. I use it for all my plants.