A few days after the first frost last week I cut off the leaves, most of the stem and dug up our dahlia tubers. While washing off the dirt they were hard like potatoes (with the occasional skewered one). I set them aside to dry in my garage (indirect sunlight, ok airflow and about 12-15ºC maybe).
The next day I came to see if they were dry. They're dry but they've shrunk a bit in size and most of them are now a bit squishy and soft to the touch. This happened last year as well and I'm not sure what I did wrong, all the research I did indicates the last dirt needs to be washed off and the tubers dried before storage.
I live in zone 5A.
What's a possible explanation as to what happened and how can I avoid this from repeating ?