Major ones I would fix are:
- your 404 page is returning a 200 status code instead of 404 (making it hard for Google to know what's a broken page)
- your server isn't compressing (i.e. gzip) any of the responses which will impact speed a lot.
- you have several broken external links e.g. one to chandlerdpethpsych.com
I used this Chrome extension (I'm the author) to crawl and find these issues if you want to check and confirm fixes: