Somethings eating me leaves!

[LauraC]

Hi all! Help needed -
I have a few plants suddenly being eaten, found lots of black beetle types around one the other day, but after spraying soapy water haven't seen any... although the eating seemed to have stopped for one day, now its back and I can't see anything around that might be the culprit! Below is what the leaves now look like (skeleton leaves now)

 

[Marck]

Greetings, welcome to the Forums.

Your Agastache is being eaten by some leaf-chewing insect, such as caterpillars or beetles. Visit the plant at night with a flashlight, that is often when hidden pests come out to feed. For one isolated plant you should be able to remove the pests by hand ...or with a tool if you're squeamish. There are organic pesticides that will work on some pests, such as B.t. for caterpillars, but not beetles.
By the way, I'm presuming you only took the plant inside to photograph it. Agastache are plants that do best outside in full sun. It won't do well as a houseplant, especially in a shady situation.