New problem! I think ph is off but im unsure of what to do.

Hey so ive been having nutrient burning issues so i decided to repot my plants and bought miracle grow potting mix and threw them in slightly bigger pots and gave them lots of water.

this is the stuff i bought .. http://www.canadiantire.ca/AST/browse/2/OutdoorLiving/FertilizersGrassSeed/SoilsMixes/PRD~0594898P/Miracle-Gro+Premium+Potting+Mix.jsp

thinking that it was great and already enriched with plant food n the mix was .14 .14 .14 so it was a pretty even mix i could then start feeding nutes into to balance correctly.

however its been 24hours and there are black spots on the fan leaves and the plants have stopped growing, so i put them back in the original soil and smaller pots trying to balance the problem but thing is i want to setup some proper soil in pots and am unsure of my mix. I was thinking of using some soil with high nitrogen and mixing it 50/50 with perilite and throwing the plants in, would this be a good idea ?

It's all a great idea.... If your wanting to kill your plants.
MG soil with extended release ferts is a BAD move, watering after transplant, another bad move.
Transplant them AGAIN, really not bright.
Keep on stressing them, of course they aren't going to grow, your killing them. Think about it man.
Your over nuting this shit out of it, it doesn't need nutes at this point.
DONT USE MG PRODUCTS, they arent for noobs, and moreover they suck all the way around, you can taste it in the weed.
Welcome to RIU
Your plants are going to show signs of overwater as well.