My Krauter Vesuvius plum tree is about 4 years old and has done really well. This year, it did not bloom (others in my area did). It also seems slow to produce leaves. Other Krauter Vesuvius plum trees in the area are covered in leaves, while mine seems slow and spotty. The leaves sprouts are there, but it seems to only be fully "popping" in some spots...It looks healthy and the leaves that are fully popped are a good color. Any ideas on what could cause this?