What are these white and brown growths on my potted Little Gem Magnolias?

I have a little gem magnolia growing in a pot on an apartment balcony. I am getting 2 different types of growths on the leaves which I am concerned about. One is white and is mainly concentrated under the leaves and the other is a brown raised growth on the top of the leaves. Can you tell me what these are (if they are harmful to my plant) and if so, how I can get rid of them. Thanks!