Hi-
I'm not sure whether qRules is needed. A default value would probably work.
For my:myFields/my:dropdown1, the default value is my:myFields/my:containergroup/my:repeatinggroup[1]/my:dropdown
For my:myFields/my:dropdown2, the default value is my:myFields/my:containergroup/my:repeatinggroup[2]/my:dropdown
Etc.
Does that make sense?