Stinky is always right about everything.... SO I would listen to her words and take them well.

Since you mentioned you are using MG soil Chances are its a PH thing. You should search for the Thread made by GKnowm about a whole grow he did in MG soil. he had to Ph his water up to 8 for watering (most Tap city wate ris 7)

The Ph of MG soil is very low. So I bet judging by the age of your plant. i bet the Ph is really out of Wack. Since Mg soil has nutrient fertilizer in it already a Flush may help but Im not sure if you'll get it back to where you want to be Ph 6.8

Check out that Thread dude,, And do the things Stinky suggests...

Good Luck

kd