This looks like a temperature/print speed thingy.
It looks to me that on those visibly different sections the print speed is slowed down because of the cooling parameters of the filament. Printing slower with the same temperature means that PLA becomes more shiny.
Silk PLA should never be printed above 50mm/s on walls. TBH 50mm/s is max on all features but you might be able to get away with 80mm/s on top/bottom. FYI silk gets shinier the slower you print it. I use 25mm/s on outer walls.