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Some more details would be helpful. What is the temperature and humidity in that area? Any air circulation (fan, etc)? Diameter of each? starting and current weight/mass or % weight loss?
Pigs are magical creatures.... they turn vegetables into BACON!!
temperature is 10 -14 c, not sure of the humidity, circulation is enclosed and not enhanced by fan etc...diameter of each is around 5cm but this has reduced to 3cm.
frankly I was hoping for just a general explanation of what can cause it
The general explanation is that the salami and chorizo lost water content. When the moisture is lost quickly, the outer portion of the salami dries to a greater degree and the salami becomes case hardened. Your humidity is probably too low.