It's call blooming and it's because certain additives added to the tire can oxidize when they come to the surface How old are the tires on the Niro vs the other Vehicle? It could definitely be difference in manufacturing process between the factories where the two different tire sets where made.
Cleaning and dressing is pretty much the only thing you can do. Apply a good tire cleaner, with a tire brush, let sit 2 minutes, rinse a lot. Dry a lot, like completely dry. Then dress again.
My go to are Meguiar's Ultimate series, because the result/quality/price ratios are unbeatable. The all-wheel-cleaner is a gel, so it will stay in place for the two minutes. I also use the ultimate shine, but in your case try the Endurance in gel, it supposed to be anti-browning. If not Meg, I'd go for Optimum, Griot, Adam's.
2018 FE, MA