Could be a couple things, I am suspicious of the MG fertilizer for that plant, it might be too much fertilizer.
The other thing is that plants going from inside to outside need a halfway house, a time to harden off. We've got some cooler weather coming and gray days. Don't let the plant get soaked, but this might be the time to get it outside.
The new growth is a great sign though, get it outside and watch it carefully, I think it will be OK.