Astilbe Leaf Damage

My previously healthy Astilbe has had a lot of leaf damage this year. The 'flesh' of many of the leaves has disappeared, leaving the skeleton of the leaf behind. I can't see any evidence of pests on it.
Does anybody have any idea what could be causing this?
TIA
Steve
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Steve said:

Classic sign of earwig damage.
If you hit them directly with some soapy water they are easily killed. However, they hide during the day and only come out at night to feed. You can either go out late at night and spray them while they are out or you can set traps for them.
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Pat in Plymouth MI

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