The story of 2 oregano plants

The plant on the left is thriving all year round. It was planted by the previous owner of our house. The one on the right was planted by me. Why is it dead?
We also had lots of parsley when we moved in, it was thriving. Soon it all shoot up into flowers and is all gone. What is the secret of a good herb garden? Everything else seems to be growing for me, just not these little buggers that we could eat.