Hi Diane, 

This is mainly a service for Wake County residents, so I would suggest you contact your Alleghany County Extension Office. https://alleghany.ces.ncsu.edu/people/

I will say that leaf drop (after spotting, oftentimes) is very common with magnolias.  People suspect they are sick when it is just the annual drop.  However, this tree does look a little thin.  It's still young, so not blooming is not really the issue, but it looks like it is lacking vigor. I would make sure it's not overwatered or gets very dry.  I see the irrigation which can be very helpful, but if overdone can cause root rots. It looks like it is getting adequate sun?

I would remove the diseased leaves, and hope that the new growth comes in and stays pretty clean. https://hgic.clemson.edu/factsheet/magnolia/

Hi, I sent the link for Alleghany Co Extension so you could contact them.