Hello. For the second year in a row now, my birch tree has started to lose it's leaves in July. This year, i started to notice the problem in the top most branches a couple weeks ago. But today, i noticed leaves in the bottom branches doing the same thing. And there is a large collection of brown, lacy leaves at the base of the tree now. The leaves lose most of their green flesh, leaving the veins and lacy remnants that eventually turn brown. Can you help me figure out what this is? Picture attached. Thank you!