There is no real issue here, you could downgrade these two packages but there is no need to as far as I know. Not sure why these two have been rolled back in the repositories, there are reasons usually, but most of the time if you don’t have any issues, just ignore it.
//EDIT: for Plymouth, the reason is in the Stable announcement thread [Stable Update] 2024-03-13 - Plasma 5.27.11, Firefox, Thunderbird, AMDVLK, Qemu - #2 by philm