Flush the living crap out of that soil.... NEVER add epsom salt to the soil, only to the nutrients. Ad @LexLuthor said its immediately available.
Also water the whole pot. You don't need runoff but now that you added that epsom salt you are going to need a huge huge flush.
After the flush because you will be washing all the available nutrients out you will want a light feed of synthetic nutrients so that they don't end up with deficiencies. You will also want to add beneficials like bacteria and mycos.
I would be tempted to rip them out and repot them in the same mix WITHOUT epsom salt tbh.