I have processed hundreds of Foma 100 and 200 5x4's without being absolutely certain that my temps were all within 20º +/- 1º and never seen such an effect on the film but I have seen it produced by scans. I suggest you get a really strong loupe and check the comparable places on the actual negative. Just saying ....
It may be worth scanning at a different resolution. In the early days of Digital minilabs Kodak had issues with their films and excessive grain when scanned, printed optically there were no issues, this was down to surface artefacts.
Usually the temperature variations have little effect with some films but a greater effect with others. John Davies the landscape photographer found that the variations in graininess of his students work shot and processed with the same film and developer, almist certainly FP4 and ID-11 was down to poor temperature control.
Many years ago I needed my portrait taken working with my LF camera in the landscape. The photographer (a friend) used a couple of rolls of Tmax 400 in his RB67. Later that evening he processed the films as I cooked, I noticed he didn't check the temperature of the stop, fix or wash, I did make a comment. I processed some 35mm Tmax 400 I'd shot with my Leica M3 in the same replenished Xtol. The next day when I went to make the prints his rolls of TMY were excessively grainy and unusable, much grainier than my 35mm TMY negative which were quite fine grained as expected. Now as I'd supplied the film and had used the batch before (and after) it wasn't storage.
One developer in particular can and will cause issues with softer emulsion films and that's RO9 Rodinal because it contains free Hydroxide. Surprisingly the worst film in Rodinal was Acros which contains Whale gelatin rather than Bovine Gelatin, there's plenty of examples of Acros reticulating badly in Rodinal, and also emulsion lifting off the base but Tmax 400 was prone to issues as well but not as severely.
Having said that I had no issues with Acros or Tmax 400 in Rodinal. I grew up processing Ferrania reversal films then E4 (E3) and the temperatures were critical to +/- 0,5º F rather hard but manageable just
Ian