I am going to reiterate a point real fast. RE-POT. The first plant looks like it has some burn damage, could be salt build up, and the second looks like it is suffering from a N defecency. MG is a good soil to use but it does need some additives. The plant food is ok as well just use in quater strength. I used 1/4 tsp. per gallon to start and then very gradually increased. People bash MG because most don't know how to properly use it. It is a powerful fert. that needs to be gradually induced to a plant. You also usually don't need to use ferts for the first month or two. The plant can usually live off the nutes in the soil so don't fert it during the first month.

Happy Toking :rasta: