alot of ppl use MG, its nt recommended bt u gota go wi wat u gt, the only prob with it is that it could cause nute burn, u have no control over the nutrients ur plant recieves.
shud think ul be ok but its all learning, nxt grow id go with the plain soil, it gives u the choices,
if ur plant starts geting nute burn then i would transplant leaving as much mg soil behind as possible and get it into some plain soil, but of corse by this time it could be too late.
gl