Here is a site that shows some diseases of hardy hibiscus.
This one talks about 'web blight'. See if this sounds like what you have.
You might also find this site helpful.
You may have a virus. I would take the precautions of good hygene in the garden. Any pruning that you do should include dipping your pruning shears in a solution of one part bleach to nine parts water after each cut.
If this doesn't help, you might want to consider taking a leaf to a good garden center in a sealed plastic bag for id.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.