Answer: White flowers sometimes have a greenish tinge when they first open, but this generally disappears with maturity. If your snowball bush is newly planted, it may also be struggling to become established while expending energy to bloom. The combination may have encouraged the premature failing of the blossoms. I don't think it is anything to worry about - next year's blooms should be just fine.
You can trim your Japanese maple any time this summer. Hold off on pruning from mid-September on - any new growth the pruning encourages won't have time to harden off before winter time.
Best wishes with your garden!
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