Hi, I just saw this thread. I'm a little north of you.
It has been my experience the last 6 years that you cannot 'leave them be' and all will be well. Not around here. You can have a wonderful booming hive one week and nothing the next.
It was a bitter lesson I learned when I got back into beekeeping.
You will definitely need to figure out a way to deal with the mites and keep an eye on the brood health. Now I am using OAV for the mites.
Sorry to hear about your hive.