Is it normal that linked clones do not see the increase in HDD space on a template?
day 1: template created with 80GB HDD.
day 2: linked clones created.
day 3: template HDD increased to 120GB, but linked clones do not see the difference.
A linked clone is based on snapshot. That snapshot was a moment in time when you did not have new space. Only new linked clones will see the new space, the old ones would need to be changed manually.