Did you try running the clock to -1004 mhz (on Linux)? or -502 mhz on Windows.
You can also flash a Palit or MSI bios on them (at your own risk). That way you can get between 34 - 37 mh/s, depending on silicon lottery. O i thought you were talking about GTX1660 Supers. nevermind this then.
This makes no difference on hiveOS using Trex miner or you have a specific miner software that works with this -1004 MHz? I don't see any difference using this settings in hiveOS for my 1660 and 3060ti they are both hynix based what am I doing wrong?
Take a screenshot of your settings in Hive OS. This will make it easier for you to help.
When you bought these video cards, did the old owner show you the hashrate or not?
The best way is to use the settings of the previous miner if you don't want problems.