CROMi-X 5.4 is the latest version - there are no updates, but it should not be "slow" - however you define that.
I never used multi-user - no idea if that has any effect....
A clean install often does help if performance deteriorates over time. Depends how long you have been running this installation.
If you flash the rom again, make sure you select "fsync off" in the installer. That gives you the biggest performance boost.
You can also try to run CROMi-X with data2sd, moving the /data partition to a fast microSD and therefor avoiding the slow internal memory altogether (you can still use it for storage).
Then look at your setup: Lots of widgets on the home screen will slow it down - period.
Check what apps you have running, maybe use Greenify to hibernate the ones not in use.
For me CROMi-X never was slow, but I have to admit: the latest version of CROMBi-KK runs better
You just have to live with a few bugs relating to the dock....