Good afternoon and thank you for your question.  I'm sorry to hear about your garden.  Unfortunately, from your photo, I cannot asses what has causes your plant to decline. I would encourage you to send a sample to the plant and pest diagnostic clinic where they will be better equipped to accurately diagnose the problem.  Here is information on how to submit a sample:  
https://ppdc.osu.edu/submit-sample

I wish you all the best.  Thank you.