Last 2 rows of keyboard are uneven enlightened after repair

Hello, I had to repair my Macbook Pro m1 14" few days ago because I spilled a coffee on it (yes it had sugar in it). The repairman changed the keyboard because the keys were stuck due to sugar caught in the mechanisms but now I see that the last 2 rows of my keyboard are less bright than the rest of the keyboard, what can cause this problem ? Note that the area where i spilled the coffee is not the same that the area that is now less bright, that's why I am confused.