theme-dependent super-slow admin

I’m using a theme (Xone) that I like and would prefer to not change… However, the wp-admin dashboard is unusably slow… it started out at around 5 second load latency and now is around 45 seconds! Unfortunately, though it is a theme I paid for, the developer has flat out said “sorry, I can’t reproduce it and so I don’t know what to tell you” without giving any tips on troubleshooting. I’m reasonably savvy with html/php and MySQL, but I don’t know where to begin troubleshooting this:

• It is dependent on the theme (goes back to normal when I switch to another theme), and happens even if I deactivate all of the plugins.
• It only happens in the dashboard (the front-facing site loads reasonably quickly… under a second or two)
• Interestingly, this only happens on my production server (I’m using my work/university server as it is a work-related site). On my local version of the site, the admin is reasonably snappy (< seconds to load)

Does anyone have advice on things I could look for in the theme files or server config? or debugging procedures i could follow to begin troubleshooting this on my own?

thanks