I think this doesnt have solution for now, the hashrate down a lot with 4 GB cards (and i already put all commands to try to get better). The 8 GB Cards are as the first day.
Ive 1 (the main) with 8 GB, and it is minning right now in 24 Mhz. The others 4gb cards from the same rig, are in half or less (12 mhz) when in the past this cards can mining in 20/22.
The 8 gb in Main is Asus Strix RX 570 8GB. Ive also other Asrock in other rig as main and its a little better (26 Mhz).
But in the olds 4 gb cards, the drop is huge (Sapp, MSI, Giga, 4 GB), 12,12,11 Mhz.
Im with Crimson Beta driver (17.X i think) by manual install, and works equal or little better that 20.X from Adrenaline.
Windows 10, Core2Quad, 8 GB DDR2, 30 GB in Virtual memory