It's now back to normal... tho I don't know how exactly I fixed it...

Here's what I did, in case somebody are facing same issue.
1.) Take 2-3 cards off, remove the riser.
2.) Plug all of them back (new order) so I switched the trouble one in new slot
3.) Reinstall driver
4.) Rollback to stock setting
5.) I'm now using 3.3b instead of 3.4 for the EWBF Miner.

Constant speed only 55-61c atm, will continue watching!