Dwarf meyer lemon tree lost all leaves
I have a two years old dwarf lemon tree bought from OSH. Last year it flowers and bears fruit. It did lose some leaves during last fall, but grew right back. This year, it flowers during March, and now I have about 5-7 fruit on my tree. But since end of April it started to lose all leaves, some curl'ed up, some just brand new w/ brown spot on it. I leach out the soil, thought it's salt burn, and changed the top portion of soil as well. Unfortunately, last pair of leaves dropped yesterday, w/ only branches and healthy fruit. What else should I do? I don't think there is any pest issue, I have been water this tree once a week, so it's always on schedule. Please help!