we recently noticed that the leaves are
starting to curl up and some have white patches.

Could be Wooly Apple Aphids.The aphids and their nymphs are a reddish brown and
they produce fuzzy white filaments in patches. The leaves can become yellowed
because the aphids are sucking insects that drain the chlorophyll from the
them. The small rust/brown spots could be rust (a fungus) or merely the aphids
themselves. These aphids are difficult to get rid of because they have a waxy
coating that is not easily penetrated. Control usually requires professional
application of pesticides.
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