Your Vega cards are hynix? That's the most weakest version of Vega cards mate Samsung and micron are the best, I also have two hynix Vega cards and one achieve 43MH while the second achieve 47MH, I will drop you my config
amdmemtweak --CL 18 --RC 34 --RP 13 --WR 11 --CWL 7 --FAW 12 --RAS 23 --REF 16000 --RFC 164 --RTP 6 --RRDL 4 --RRDS 3 --WTRL 4 --WTRS 4 --RCDRD 20 --RCDWR 11
Things will get easier for you if you use hiveOS instead
You can just copy my tweak and insert in OC settings in hiveOS, also switch on
aggressive undervolting and insert my amdmemtweak into tweak section