Did you find it necessary to do stretch and folds before dividing and refrigerating?
Next time, you could reduce the amount of IDY, or use cold water to get the finished dough balls down to a finished dough temperature below 70 degrees F, or some combination of both. Keeping the dough balls in the coldest section of the refrigerator will also help. You might also leave the dough storage container uncovered in the refrigerator for about an hour before putting the lid back on. If the finished dough temperature is too high owning out of the mixer bowl (or after hand working), you can cool off the dough balls even faster by putting them into the freezer for about a half hour before placing into the refrigerator compartment.
There is no harm if the dough balls double or even triple in volume after five days of cold fermentation but you don't want them to overferment.
To give you an idea as to yeast quantity for a five-day dough (with an outside window of almost 8 days), when I came up with my clone of the Papa John's clone dough, which is a roughly 5-8 day dough, I used about 0.16% IDY. PJ is careful to keep their dough cold at all times, from its commissaries to its stores, but without reaching the freezing stage, as some competitors have alleged.