We planted grass a couple years ago in our backyard. The yard had been mulched for years before. It’s a shady area with trees and the grass we planted grew nicely last spring at first. Then, in some parts of the garden, brown spots started appearing mid-summer in various parts. We fertilized and watered and applied fungus treatment, but the brown spots continued. And now that the snow has melted, I can see that the brown spots have progressed during the cold months. In some brown parts, the grass can be pulled by hand very easily, as if the roots were dead and in others, it is still well rooted. What can it be? Could there be multiple things going on? And what can we do? Thank you.