You need to flush that soil with 2-3 gallons of water. Plants grown from seed should not be fed nutes for the first 2 weeks. Having them grow in very rich soil(which MG soil is very hot) will cause all kinds of problems, unless you really are experienced at growing in soil and understand soil nutrients very well. The problem is the time release of the nutrients can cause swings in nute levels and can cause the PH to get off, cause nute lockout. If you really want to use MG soil, it is best to get the nonnuted kind and create a root ball area of non nuted soil, then transplant into the nuted soil after a couple weeks and allow the roots to grow into that soil in search of nutes.
You shouldn't have to add any nutes to MG soil for the first 4-6 weeks(after transplanting into the nuted soil). You most likely have caused a nute toxicity with all the chemicals in the soil and the plant is freaking out. Flush it with fresh clean water, 3 times the amount of the soil that you have(for 1gal container use 3gal water)poured slowly into and through the pot, and let the runoff go into the yard.
After you have flushed it, let it sit for several days to dry out before adding anymore water.
