one, when using fresh, quality potting soil, adding trace elements isn't needed. if you really think you have mag deficiency bury a galvanized nail in the soil (same works with standard nails for introducing trace amounts of iron...which is all that's needed anyway). i use nails of both kinds to pin the flagging with whatever plant info is needed written on it (strain, date started, fert schedule, etc) down to the soil so i can keep better records of what's been done when and where.
second, miracle grow (read the bag info!) potting soil already has time-released ferts in it and adding more will be too much for a plant easily susceptable to fert burn and overwatering. and yes, it needs to be transplanted. watering every other day in a pot that size with a plant that big can't be enough...unless maybe you're soaking it and the drain holes are plugged.

you were told all this already yet you still continue on your current course? being happy with your plant during veg is one thing but what's really important is being happy at harvest. if you want to turn things around you'll need to listen to straight-up experienced advice sooner or later...

http://users.lycaeum.org/~sky/data/mjgrowers.html

good luck and get busy!