Why would 2 doughs split from a single mass, develop differently once in the fridge? This happened to me last week as well...

I've been using the same recipe for weeks. I divide the mass into 2 individual balls that I form up and place into pre-oiled containers, then pop into the cold box uncovered for 60 min, then snap the lids on tight. Invariably, one will appear (at least to me) to have developed more than the other, more bubbles are visible. I typically stop mixing around 79-80 so I can put them to bed at close to 80
o.
Could a degree difference between the balls cause this? Position in the fridge? Thanks!