Just something I found out the other day when I bought some juniper material, and I'm sure leatherback or auk may or may not know if this is right. The lady knows her stuff.
There was another juniper there that had just a few white spots and she showed me incase it happened on mine. She took a paintbrush and using methylated spirits brushed the affected area. Meths as we know evaporates so I'm sure it does no damage to the foliage?
I noticed some brown sections on another I got tonight. It's merely material but would it be worth me cutting away any affected areas to be sure? There's not much and I didn't spot any white spots (bit it is late lol) I will look better tommorrow when it's light. At first I assumed it could be down to it being so dense that this foliage is not receiving any sunlight.