If you read stinkyatticks sticky thread about Epsom salt, she will tell you Epsom should not be used to cure a calmag deficincy. You really need to cure it by adding calmag. You really need calmag. If your still in veg and have a lil vegging to do then you should be ok but if flowering your not going to build beautiful sugar/photo leaves cause they are going to eat themselves and brown up more causing loss of yeild. Also when flowering calmag deficiency will cause weak stems and fluffier buds rather than a strong stock.