I have installed Query Monitor.
The db queries take 0.5s of the 30.3s page load time for the edit product page.
There is one error relating to a missing dependency for Redux. Redux-admin-css (missing)
but this is occurring on every page in the WP dashboard.
I went back to look at plugins, and removed slider revolution 6.09 and now back to 3 seconds load time for editing products!