You don't need to correct the situation where one of more of the files has expanded because on restart of SQL the files will be back to their defined size. If both files have a sized defined in the system catalogs of 1GB, then after a restart of SQL they will both be 1GB, regardless of what they automatically grew to before the restart.

Also, if the files are sized the same to start and have the same growth increment, proportional fill will ensure that they fill at the same time and they should all grow at the same time.