How did I over-dry?

You could have went into your dry phase with your flower being too dry. Old timers would sometimes start sunsetting their watering schedule such that the buds are beginning to lower their moisture content before being cut - I used to do this but found it to be an unneeded step that aggravates your real dry phase. Wet trimming, in my experience, is not worth the trouble. I greatly prefer to do any perturbing of the plant prior to cutting them down, so any fan leaves that would be trimmed wet get pulled the week or two leading up. Not only is it easier to trim, do you save more hash, but it also modulates the drying of the flower to an extent (this is the mechanism behind flavor chasers always seeming to fall on the 'whole plant hang' style, as then the fan leaves and stems really temper the drying and slow it down even more). If you had normal-moisture content bud going into dry, and truly held at 60F/60RH, then your dry should have been 10-12 days anywhere in the world with basically any strain with flowers of any acceptable density. For example, where I live the humidity outside can range from single digits to low 80%s depending on the time of year. The same tent, with different equipment, has me between 55%RH-60%RH between 55F-65F depending on time of year. This results in a 10 day minimum when running the 55%RH bottom threshold. In summary, with a 7 day dry expect a harsh/sugary/chlorophyll-laced taste to the flower for the first few months of cure. The way it was explained to me is large humidity dips early in dry can effectively lock sugars and chlorophylls into the plant matter, making your cure take longer. Taste your flower to confirm this. If you really are feeling adventurous, a water cure can fix this at the simple cost of all your terp content.