Yes as the soil difference. Mine has been depleted as well. This was one of the things I learned when Rick Tasco and Roger Duncan were in my yard. I need to replenish the soil of it's nutriants. I plan to be doing a major overhaul and adding new and super rich dirt to the beds. The other thing is that my pictures were in a shading area which may not have helped.
Still; the yellow on your "falls" is wonderful!
