The more information you give us, the better help we can be. It's always important to give your location. There are hardly any garden questions that can be discussed without regard to location/ climate. But then more about the conditions your plants have been in - has it been very rainy, how much sun do they get, how have you been caring for them re watering, fertilizing, etc.
But to start with, my guess would be disease, not insects. The clematis most likely has clematis wilt, a fungal condition that they are prone to. I actually gave up on trying to grow clematis in containers, because they always got it.
Here's an article about it: https://www.missouribotanicalgarden.org/ ... -wilt.aspx
A couple highlights from that article:
This organism appears to be activated by high humidity and favorable growing conditions found in early summer. ... Prompt removal of diseased stems. In the event that plants become infected, cut diseased stems just below ground level and destroy them. Spray any remaining, healthy parts of the plant and surrounding soil with a protective fungicide
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