Magnesium Deficiency

I think I have magnesium deficiency in my three 6 week old plants, is there any household product I can add that would fix this or do I need to buy something like epsom salt or dolomite. I read about using molasses, would that work?

Do you know for sure it's Mg deficiency? Or could it be a Ph imbalance, causing Mg Ca lockout? First,describe the system and the environment. ie.. soil or hydro. Temps,day night. tap or RO water. what type of nutrients, and what is the ppm, lighting.

I am using 4 40 watt 4ft fluoros. The soil is organic miracle grow mixed with some perlite. The temperature is around the mid 70's. I have been using some Schultz plant food 10-15-10.

when you prepared your soil, did you ad any lime?

no, just organic miracle grow and perilite