The only way ur gonna kill these plants is if they continue to grow the way they are, it doesnt seem to me that the grower knows his/her nutes, First of you shouldnt have to add epsom salt, just incase u get a lock out you would, i think that if there is a lack of Mg there is probably a lack of other nutes aswell, that yellowing looks like a N def. that darker region on the plant looks like a phosphorus def. Maybe its over fert. or bad water. transplanting the plants can only help Your leaves should be a solid some what light green, any other color means something different.