Bought this frangipani for my bf about 1.5 years ago, has struggled to grow more than 3 leaves at a time. Eventually they all fall off and it starts over. Recently, it’s been looking lovely (last few months) but I just got back from a few days away and it has a couple leaves that are looking yellow/ brown spots. In the past, we have fought spider mites off of these guys. He sits in a partial sun window. Help!