- Modded Bios and forgot to run pixel clock patcher when system config changed (like a new mobo or reinstalling drivers).
- Forgot to turn on 4G Decoding in the motherboard options. (Depending on the manufacturer, this may be called something different like 'Extended Memory' for example).
The hashrate being 18mh/s when its supposed to be 30 is easy, you reinstalled/upgraded the gpu drivers and forgot to switch on the Compute option. You have have inadvertently upgraded to the newest drivers from blockchain drivers and didn't realize that you need to now turn on this setting when mining in AMD Radeon Settings for each card.