Actually it appears that the pH is somewhat closer to 7, but I'm using one of those light/moisture/pH meters that I'm a bit skeptical of. I started using the guano/molasses tea pretty recently, mixing 1 tablespoon of guano and 1 teaspoon of molasses per gallon of water.
I'm attaching another picture of the scale I'm finding on the leaves now. Haven't seen anything like it before, so not sure if it's from bugs or if it's contributing to the decline. Thanks for your help