Hey all!

We planted a "Red Fall" apple tree (about 6' tall) about a month ago.
Tree seems healthy, but we recently noticed that the leaves are
starting to curl up and some have white patches. These patches look
dusty, but aren't. There are also a few leaves that just turn yellow
and come off the tree VERY easily. Finally, I've also noticed some
leaves have some small rust/brown spots.

We're zone 3A in Calgary, Alberta, Canada.

We haven't had much luck finding a decent "plant diseases and pest"
book or website.

Any idea what is happening and how to deal with it?

Thanks!