:yeahthat: yeah, i agree. it sounds like a high ph problem, i had the same,kinda brown/yellow spots on all my fan leaves, i thought it was spider mites at first,as an infestation of them has the same characteristics but i got the old microscope out and saw none of the lil` critters.
i suggest you water less-i.e wait a good 3-4 days before watering each time.
i am also using MG soil and i don`t add any other nutes whatsoever, and my gals are great, a couple of the lower fan leaves look like nute burn,but the rest of her is budding like crazy!
deffinately get some epsom salts,or mix lime in with your next soil mix as this gives the gals Magnessium, and acts as a ph buffer among other things like calcium etc.
MJ uses loads of Mg,and a lil` spray with some epsom salts-dissolved in warmish water will perk the ladies right up. don`t over-do the Mg as this can lock up other essential nutrients too.
good luck dude, your doing well. maybe try a good flush first, then go at them with low nutes high in "P", around 1/2 strenghth. see what happens. the majority of first time growers screw up because they "over-attend" their crop instead of just letting them grow.
hope this helps man.
cheers,:spit: Shuggy.